•Put diversity in your teams! Don't have two Pokemon with the same type in your team, it will create multiple weaknesses, and cause you easier losses. An example of a well balanced (Type Wise) team:
Blastoise
Infernape
Umbreon
Espeon
Frosslass
Staraptor
•NEVER put more than one type of a move in a moveset. Unless the other move is a stat/support move. An example of a bad moveset for a Kyogre:
Waterfall
Surf
Water Spout
Hydro Pump
Though every move is powered up by 100%, but it only hits super effective on several types. An example of a good moveset for a Kyogre would be:
Surf
Thunder
Calm Mind
Ice Beam
•ALWAYS EV your Pokemon. If your Pokemon aren't EV'ed, it makes battles one sided and boring... EV's are VERY important in battling and should be used. I will not teach you about EV's in this tutorial, but you can search Google for some good tutorials.
•Make sure the Pokemon you're using has a good nature. I cannot stress this enough, I have seen trainers who go, "0mGz Lo0kZ aT mY aWeSoMe PoKeMaN!!! i'M tHe BeSt!"
But when I battle them and win, I find out their Pokemon have horrible natures. Natures DO effect stats, which need to be payed attention to. You don't want a Rotom with low Special Attack, but a high Physical Attack when its movepool is limited to Sp. Attacks. The example I used was a Rotom with an Adamant nature.
You absolutely need the right nature! Find a Pokemon's base stats, then find the highest one (Not including HP), and get it a nature that powers up the stat. Natures are covered in the EV guide.
•Don't just fill up your Pokemon's moveset with all combat moves, use stat and support moves too! Example of a Lucario moveset that uses a stat-up move.
Swords Dance
Extremespeed
Blaze Kick
Close Combat
Yes, yes, the whole moveset sucks, I know. Swords Dance will raise Lucario's attack sky high. A support moveset for an Azelf (Not Uber, but this Support needs strategy to use)
Stealth Rock
Taunt
Psychic
Explosion
Use Taunt to stop the opponent from Stealth Rocking then use Stealth Rock youself.
Those are just examples. You can do whatever you want.
•Don't use a whole team of ubers, and call yourself unbeatable. The thing I hate most is battling people on Youtube, who send out ubers, but still get beaten cuz they can't EV.
A battle guide I wrote in 20 minutes the other day. :) It's kinda short but those are mainly basics you need to know.