Here are a few of the several steps to becoming an expert battler in the wonderful world of Pokemon.

1. When building a party, feel free to be random, the weak can be the best.
2. Follow a pattern, if you don't like having to do different things everyday, just make a pattern. (ex. Everyday, I train at the stadiums in Nimbasa and then breed 50 eggs)
3. Talk to everyone in-game, people around the map will give you various items that will save you in the future.
4. Set a goal. When you're training, try to set a party base level, so training only becomes a strive rather than a stress.
5. Pay attention. Storyline hints are usually, in most rpg's, told through text by NPC's (Non-playable Characters).
6. Practice. If you're not sure your pokemon is strong enough, test them at the Battle Subway.

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Notes for those wishing to battle competitively online

1. Strategy. Best way is to plan out your pokemon before you catch, breed, or trade for it.
2. Natures. Certain natures lower stats and raise stats. On SS/HG/B/W, the lowered stat is in light blue and the raised one is in red.
3. EV's. On Black and White, the EV's are simple to get, being some routes have a 100% rate of having a certain pokemon. If you don't know what EV's are, Smogon, Serebii, and Bulbapedia are good sources for information.
4. IV's. Once you have your EV's put in, find an IV calculator, I find Psypokes's calculator better since you don't have to figure out all the extra stuff.
5. Coverage. Having 6 of the same type Pokémon with the same moves won't do you too much good, you need to be able to take down all variations of foes.
6. Plan. On B/W, you get to choose the placement of the 6 pokemon in your party and also see the opponents party, this gives you an advantage to put the right pokemon lead.

That's all I have for now, there are tons more though. Hope this helps. Thanks for your time!