Yoshi is my favorite character to play in the 64 version. There is so much you can do with Yoshi. Yoshi is god with his tilts and aerials. Sex kick is... well, sex kick. Not a move I use a lot, but it is good if you need to keep them away from you and don't want to use fair. Utilt is used as a launcher or a chain to most of his combos (for example, come in with dair or fair, utilt, fair to chain into another dair to utilt or simply bair) because it's fast, hits a wide range, launches them perfectly, and cancels basically any attack that's not a Donkey punch or Falcon punch (although I have seen it happen). Ftilt is used to set up spikes. This move, at anywhere from 30-70ish percent on most characters, will launch them right into the sweet spot for fair - if you do this by an edge, it's game over. If not, you smash them into the ground and follow up with either a dair to utilt combo starter or a dtilt to running tackle, which normally sends them flying across the screen. Dtilt - I originally found out how powerful this was from messing around with Yoshi on Hyrule. At 0%, it can knock them 3/4 the way across the main platform, and it does 10%. It's amazingly fast, and Yoshi looks funny as **** when he does it (hold down. tap a. laugh.) As if enough hasn't been said about the fair already, it's one of Yoshi's best moves. Spike, part of most of his combos, fast recovery if you time it right, there's not much bad about this move except the fact that you can miss if you don't practice. Which you all do. Uair - it's not quite as good as Fox's uair because it stops you from moving upwards, making it extremely hard to hit someone with it if they try to jump away from it, but it is useful once in a while - nobody expects it, so you can get some kills once in a while off of the fall from a utilt. Bair is a finisher and an all around power move. Utilt to bair is will send them flying at anywhere above 30%, and this is also a good move to advance with (turn your back, jump back, bair, repeat). Good to edge guard with, but don't get too cocky - you'll die easily. Dair is a good move, but remember not to overuse it. The best part about this move is that it can deal about 40 damage on its own if you hit with every part of it. So if you can get your opponent under a platform and utilt, they will fall right into the range of your dair - quick 50+ damage. Also useful to put in after a launcher move (ftilt or utilt). Never use off the edge. In fact, the only move you should use off the edge ever is your fair or bair. Sometimes it's good to egg spam off the edges (hang on a cliff, tap down, jump until you're above the edge, egg, grab edge, repeat), but it's not nearly as useful in this game as it is in ssbm. Yoshi's b moves: Down b is useful after the ftilt, fair chain, as it sometimes hits them and normally has less recovery than your opponent (or about the same). Also useful for catching ledges. Up b is killer. If you learn how to aim this, it becomes your primary follow up to hitting someone off the edge and long range game. Neutral B is practically useless, except as a surprise attack. If you do manage to catch them with it, immediately jump above the egg and do your down b. It should catch them as they struggle out of the egg. Do not throw with Yoshi. Period. As for smash attacks... Usmash is your best smash. Long range, huge damage, high knockback, speed... it's an all around killer. A particluar favorite combo of mine at the beginning of the game is dair, utilt, usmash. Dsmash is not as good as dtilt, but it serves its purposes. Particularly useful when in a roll war, but if you can aim a dtilt correctly, that's still better. Fsmash and bsmash are nowhere near as good as Usmash, but they do have high priority and send your opponent far - it's just that they're so easily avoided and can be countered rather easily. Stick with bair and usmash for fiishers. Running tackle is Yoshi's ace in many situations. There is almost nothing bad about the move, except for the fact that it can only be used to end a combo, not start one or chain one.
And I think that's about it. I'll update later.