ahaaaaaa!
well tournaments I will tell you right now are 90% mental and 10% on how good you are. If you go into a match against an impossible match-up (ie. the entire cast) your most likely going to lose. probably because you'll be thinking about how bad they're going to own you, as soon as that crosses your mind you fail. You have to be thinking that you have a winnable chance (by the way this applies if your playing a "big name") or chances are slim that your going to win. Ways to get over this depression and gayness is to either say to yourself before the tournament that your going in to do YOUR best, or use weed
my personal favourite.
Most importantly believe in your character. If you don't believe that Falcon is good, drop him. If you can actually see potential in him then you have a fighting chance. That's probably why people like Niko use Peach, is because he SEES potential, and tries to utalize it.
as for playing technically good, practice is the only thing I can say. go to weekly practices or smash events in your area, don't care about placing, just go in for the experience. And it is important to know ALL of your characters specific techs, like the mock-waveland (seriously I danced around MK's with this)
that's the basic gist of things:
play at YOUR best (don't aim for a placing)
Believe your character is good
Practice
Know YOUR strats
Patience............