you need to know when fair kills and when uthrow kills
if you get someone off stage you need to figure out how to use upb to get to the ledge fast from anywhere to steal their cookies when theyre recovering
once you get a fair you can combo pretty well if you have the tech, practice and try different things - pay attention to what combos and what doesn't
m2's neutral sucks so get good at what you can, be able to wavedash at any length, know when to dash back and when to wavedash back, learn when to approach
nair seems like a great thing to do in neutral a lot, especially if you watch good mewtwos play, but its just because it counters certain airborne styles. Does not work well against crouch cancel characters or other opponents who like to stay on the ground and use tilts. Against those opponents abuse movement and grab
don't stand still and hold sheild and try to get sheild grabs unless your opp is a dummy who keeps approaching you're going to get rekt
that is all