I traditionally play as Yoshi, but recently I've also had some practice with Jigglypuff (for the lulz). Apparently the common opinion is that Yoshi sucks, but I do quite well as him (thanks in no small part that I've been playing him for years).
The group for some reason will almost always do Fox's stage (the big, long ship with no floating platforms that I can egg people from under), and when they don't do that one, they do Link's stage (the Hyrule castle place that occasionally spawns a tornado). Any other stage seems to make people very angry.
I am not a particularly technical person; from what I've researched online, apparently "high-level" people will have every combo, move, and number memorized by heart and instinct. I do not do this. My tactics go roughly as follows:
With Yoshi:
Ground Pound (down B) is my attack move of choice. I can either go over someone and use it or time it as they're rushing towards me (if you press the move while on the ground, Yoshi will move a horizontal distance before coming down). It is fast and generally hard to block, but there's a significant downtime in which I can get hit after I hit the ground, which means that it's less useful in 1v1s where the opponent will focus all of their attention on me.
Egg Throw (up B) is one of my favorite moves. The N64 eggs have significantly more explosion radius and knocking power (in newer games, the eggs simply do damage), although the N64 attack is MUCH slower, making it only useful for longer distance encounters. I also find that most people aren't used to opponents who use the eggs, probably because it's hard to get used to aiming the arch projectile. The egg works well for damaging/interupting an opponent as they try to jump over me, harassing people who are on platforms above me, and doing serious damage to opponents as they helplessly try to get close to me.
Egg Lay (B) is rarely used, but sometimes I'll use it in encounters when the opponent is vulnerable (not jumping or hitting me) or when they're near an edge (surprisingly, some people don't know that they can direct the fall of the egg).
Headbutt (side A) is useful for encounters where the downtime of pounding is impractical, and can do some serious damage.
Yoshi's jump is amazing, and he doesn't particularly need a third jump most of the time.
(In melee/brawl, Egg Roll is also useful for damaging the opponent, although if I accidentally fall off the edge while using it, I'm dead.)
For Jigglypuff:
Throw (R) is useful for Jigglypuff, unlike Yoshi. It is good for doing damage and harassing opponents, but is unfortunately not particularly useful for killing blows (like most throws are) as Jigglypuff's throw only goes vertically.
Occasionally I will try a sing-rest combo if the opponent makes themselves vulnerable to it, but this is rare, and I sometimes miss with rest even with a sleeping opponent.
Besides that, I mainly try to wear the opponent down by punching/kicking them, while using Jigglypuff's relative speed and aerial ability to avoid damage to myself.
(In melee/brawl, I can also hit opponents with Rollout, but there's a serious risk of accidentally slipping off the edge if I miss the opponent, which equates to certain death, like Yoshi's Egg Roll.)
Generally, my strategy results in me winning, but I've noticed the following issues:
Captain Falcon is the bane of Yoshi. His Up-B grab apparently overrides pounding, and Falcon Kick (down-B) overrides eggs and usually results in me getting hit. His speed makes it difficult to land a decent hit on him. How do I compensate for this?
I cannot for the life of me figure out how to aim Jigglypuff's rest attack. I know that you have to be RIGHT NEXT to the opponent to make it hit, but often I find that I can literally be as close as I can get to the opponent and rest will still miss. Why?
Is there a way Jigglypuff can defend against attacks from below while in the air? Too often I wind up getting kicked upwards off the stage mid-flight.
Any tips?
None.