Spin Attack
By simply jumping with A, B or C, Sonic or Tails coil up into a spinning ball of doom, and you will probably be using it to dispatch most of the enemies in the game.
Spin Dash
The spin dash first appeared in Sonic 2. It's a handy move where Sonic or Tails first crouches on the ground and then spins in a ball on the spot, then suddenly shoots off rolling across the floor in a burst of speed (I have no idea of how the physics of that works, but who cares?). By pressing Down + A, B or C, the spin dash is started, and by tapping any of the buttons while coiled up, the spin dash is 'charged up' and you can go faster. Letting go of down will send you on your way.
  

Rings
Rings are Sonic's staple diet - get a single one of these to avoid being killed when you are hit. You can even pick up what rings you drop! Get 50 to activate a star post (or activate Super Sonic, should you have him) Get 100 for an extra life.
Monitors
Monitors are TV-like boxes that lie about in most stages. Simply jump on them to get whats inside. Here are the variations that you can find:
  • Power sneakers: These new shoes give you a temporary boost of speed.
  • Super rings: What's better than a ring? Ten rings! Get a ring-motif box be rolling in jewellery.
  • One-Ups: Jump on a box sporting Sonic or Tails' mug to get a useful extra life.
  • Invincible: Jump on the star design monitor to get a handy burst of invincibility.
  • Shield: Boxes with a blue circle on them give you a shield, protecting you from damage for one hit without losing any rings or your life.
  • Teleport: (Multiplayer Mode Only) Switches Sonic's position with Tails
  • Eggman: (Multiplayer Mode Only) Injures you, taking your shield, rings or life. Nasty.
  • Star Post
    Star Posts act as markers in the levels. Touch one and die later, and you'll return to it instead of the start of the level. Touch one with 50 rings to open the special stage.
    Chaos Emerald
    The Chaos Emeralds, handy plot devices that they are, are super powerful gems that can be collected in the special stages. Collect all seven to get the games true ending, and the über-nifty Super Sonic.
    Egg Battery/Prison Egg
    Jump on these at the end of each zone to free all the animals inside.
    Springs
    Springs launch you high into the sky, helping you reach upper parts of the level.
      

    Japanese name: Stinger
    English name: Buzzer
    Location: Emerald Hill Zone

    Buzzers mooch around in the Emerald Hill Zone. They move around slowly left to right hovering in the sky, and occasionally shoot a small fireball at your general direction.
    Japanese name: Aiai
    English name: Coconuts
    Location: Emerald Hill Zone

    Coconuts hang around on the trees of Emerald Hill, and then lob coconuts at you when you aren't looking.
    Japanese name: Gabuccho
    English name: Masher
    Location: Emerald Hill Zone

    Mashers act in exactly the same way as their older brothers Choppers. Over bridges and open stretches of water, they jump up from nowhere and try to get a hedgehog or fox appetiser.
    Japanese name: Grabber
    English name: Grabber
    Location: Chemical Plant Zone

    Grabbers lie quietly in wait on the ceilings of the Chemical Plant Zone, waiting for anyone to wander past and act as the proverbial fly to the spider. When you run underneath them, they scoot down and grab you. From there, they hold on while flashing red. Very soon, they blow up, with you attached to them!
    Japanese name: Randaa
    English name: Spiny
    Location: Chemical Plant Zone

    The squat Spiny will stick to the walls, ceiling or the floor, and simply fire energy balls at you when you speed past.
    Japanese name: Handrill
    English name: Grounder
    Location: Aquatic Ruin Zone

    Grounders tend to stay behind the brick walls in the Aquatic Ruin, and pop out when you least suspect it. All they do is attempt to run into you, like the elder Burrowbot. You can tell where a Grounder might be hiding by there being a bunch of different coloured bricks in the wall.
    Japanese name: Punpun
    English name: Whisp
    Location: Aquatic Ruin Zone

    Whisp always travel in numbers. Generally coming in threes, all they do is fly around and try to hit you.
    Japanese name: Piranha
    English name: Chop Chop
    Location: Aquatic Ruin Zone

    These little fishies swim aimlessly about under the water, that is until they see their food drop by (that is, you). Alter their eating habits by jumping into them.
    Japanese name: Gaadon
    English name: Crawl
    Location: Casino Night Zone

    The only enemy in the Casino Night Zone, the crap-like Crawl wanders around slowly waiting for you to turn up. When you jump at them they bounce you off with their bumpers. They do the same when you try to roll into them, so the only way to get to the chewy Crawl centre is to attack them from behind (in the most honourable way, of course).
    Japanese name: Saura
    English name: Rexon
    Location: Hill Top Zone

    Rexon have long spindly necks and large, round bodies and are otherwise completely concealed in the lava. The only threat a Rexon poses are the small energy balls it intermittently shoots at you, otherwise they tend to be quite handy makeshift platforms.
    Japanese name: Shinshin
    English name: Spiker
    Location: Hill Top Zone

    These guys walk around on the ceiling with snazzy cone-shaped hats, but this ain't no fashion statement - as soon as you walk out under them they shed their spiky headwear and fire it downwards towards you! When it's gone, they're vulnerable.
    Japanese name: Gola
    English name: Ghora
    Location: Hill Top Zone

    These guys are the fiery big brother of the Uni Uni from Sonic 1 - The little orb with eyes is more dangerous than it looks, as it has four red-hot fireballs that it isn't afraid to throw at you. Avoid becoming a grilled by dodging their slow pitched throws, and attack them when they're defenceless. Which is the honourable thing to do.
    Japanese name: Flasher
    English name: Flasher
    Location: Mystic Cave Zone

    Flasher mooch about waiting for you, ready to strike up an electric charge that'll hurt you even if you jump at them. Attack when they aren't glowing.
    Japanese name: Zakiin
    English name: Crawlton
    Location: Mystic Cave Zone

    Looking like a Caterkiller's shy cousin, these spiky bugs hide in the rocks mostly concealed until they decide to suddenly shoot out and hit you, only to hide back from whence they came. Counter by giving them a good smack in the face.
    Japanese name: Shiidora
    English name: Aquis
    Location: Oil Ocean Zone

    These sea horse look-a-likes are remarkably irritating - they fly around pretty much anywhere (out of water, just in case you were wondering), and fire quick and accurate pellets at you. Hit them before they hit you.
    Japanese name: Octa
    English name: Octus
    Location: Oil Ocean Zone

    Octus sit around on the floor until you turn up, then they launch into the sky and fire an energy ball at you (like most octopi).
    Japanese name: Terustar
    English name: Asteron
    Location: Metropolis Zone

    These starfish-type critters sit perfectly still until you draw close, then start flashing ominously. Rather than this being a rather lame attack, it's a precursor to it blowing up, shooting spikes in all directions! If you see one washed up at the beach, run!
    Japanese name: Kanipunch
    English name: Shellcracker
    Location: Metropolis Zone

    To say a Shellcracker is unable to turn around would be cruel - they prefer directionally challenged. Shellcrackers sport a hefty telescopic arm on their left side which can certainly give you a few bruises, but on their right they are completely defenceless.
    Japanese name: Kamakiller
    English name: Slicer
    Location: Metropolis Zone

    These mantis robots are a firm competitor for the Most Annoying Enemy Ever award... they can't walk, but they can fire their pincers at you, and they're a very accurate shot. They also have the nasty habit of waiting on top of long climbs, and hit you just when you get to the top. Hit them when they've fired off their pincers.
    Japanese name: Dousun
    English name: Turtloids
    Location: Sky Chase Zone

    Turtloids consist of two turtle robots, one pilot, and one larger 'bot that fires energy pellets at you. Take out the pilot and you have yourself a handy platform in the sky (But what are turtles doing there in the first place?).
    Japanese name: Barukiin
    English name: Balkiry
    Location: Sky Chase Zone

    Balkiry are fast moving jet-shaped bird robots. Make sure they don't fly into you!
    Japanese name: Potosu
    English name: Nebula
    Location: Sky Chase Zone

    These are best described as 'weird floaty spike bomb dropping robots', and can't be described as much else. Don't get beneath one, our you may have a few more spikes in your head than you did before...
    Japanese name: Kokekkou
    English name: Clucker
    Location: Wing Fortress Zone

    Perhaps rather aptly, the egg firing Cluckers are the last robots you'll see before the Death Egg. The vulnerable head will pop up from small turrets on the ground. They can't turn around (are directionally challenged) in these turrets, so just avoid their front ends and you won't have egg on your face.
      

    Use your spin attack on most enemies, but not those with spikes on their heads. No enemy is invincible, so experiment with rolling into them and watch their attack patterns.
    Always make sure you have rings before a boss battle. It's much easier to win of you have more than one chance between you and the great highway in the sky.
    Collect lots of points - Every 100,000 gets you a continue (an extra three lives after you get a game over). These come in handy for those later levels.
      

    50 rings are needed to activate the Star Post special stages.
    7 Chaos Emeralds are needed for Super Sonic and the 'good' ending.
    You get a 1-up when you collect 100 rings and 200 rings. If you lose your rings, you don't get another 1-up for collecting them again.
    50 rings are needed to activate Super Sonic (w/ 7 Emeralds).
    100,000 points get you a continue.
    You get 100 points for defeating an enemy.
    You get 200, 500, then 1000 points for then hitting enemies in succession. You keep getting 1000 points after that until you break the cycle.
    Beating a boss gets you 1,000 points.
    Time Bonuses:
  • 0:00-0:29: 50,000
  • 0.30-0.44: 10,000
  • 0:45-0:59: 5,000
  • 1:00-1:29: 4,000
  • 1:30-1:59: 3,000
  • 2:00-2:59: 2,000
  • 3:00-3:59: 1,000
  • 4:00-4:59: 500
  • 5:00-9.59: 0
  • Rings required for each special stage:
    Special stage 1:
    Section 1: 40 rings
    Section 2: 70 rings
    Section 3: 130 rings

    Special stage 2:
    Section 1: 50 rings
    Section 2: 100 rings
    Section 3: 140 rings

    Special stage 3:
    Section 1: 50 rings
    Section 2: 110 rings
    Section 3: 160 rings

    Special stage 4:
    Section 1: 40 rings
    Section 2: 110 rings
    Section 3: 150 rings

    Special stage 5:
    Section 1: 50 rings
    Section 2: 90 rings
    Section 3: 160 rings

    Special stage 6:
    Section 1: 80 rings
    Section 2: 140 rings
    Section 3: 210 rings

    Special stage 7:
    Section 1: 100 rings
    Section 2: 150 rings
    Section 3: 190 rings