I never really new what the nature did for a long time, like I only found out what it did recently ish.. But I still don't care about it, it could have 'pee pants' nature for all I care, if if it's a Pokemon I wanna use, I will.
How I train, my technique is just Kill all humans-I mean Pokemon- I mean.. Battle nicely.. I level up my Pokemon evenly, I don't like it if they are all mixed different levels, if the highest is lvl 60, and the rest are lvl 45, I will level them all up to 60. I'm not very good at grinding, so I just battle in high level areas, or if I'm up to it, the elite four. If a pokemon is low level, but the rest are high, I will give him an exp.share, and level him up 'till he/she is ready for the big time. (I do this also for pokemon I just wanna evolve to fill up my Pokedex)
When it's a new game, and I'm trying to find my perfect team, I wont just use the best pokemon I'm finding on the way and try and fill up my slots early, I will catch them, but I wont use them. (Eg, I'll have my beginner and one other Pokemon I know is gonna turn out good). That way, I wont waste experience points on those other pokemon, and the ones I'm focusing on will level quicker, and eventually I will have chosen the team I wanted and fill up all the slots with awesome-ness.
So yeah, that's me. :)