I'm planning on buying Heartgold next week, and I have a few questions about the Pokewalker.
1. Does the Pokewalker have to be attached to your belt in order for it to gain watts/steps? Would I be able to leave it in my pocket or bag and it will gain watts/steps?
It works fine in my pocket! I wouldn't count on it being accurate for how many steps you've taken, but you do gain steps.
2. Is it possible for Pokemon to evolve or learn new moves while they are in the Pokewalker? If I read correctly, Pokemon gain levels and happiness while they are in the Pokewalker, so when they reach the required level/amount of happiness, would they evolve or learn any new moves?
Thanks in advance!
Your pokemon you take with you in the pokewalker will gain xp up to the amount required for it to be the next level. If it's level 1, you can ONLY gain enough xp to go to level 2, etc. You can, of course, transfer it back to your game and into the pokewalker so that you can then go from 2->3, but you need to do this for each level.
Pokemon that level with the pokewalker do NOT gain new moves and do NOT evolve. If you missed a level up move, you can use the move relearner (and pay a heart scale) to get it. Leveling once normally in-game can get the pokemon to evolve, if it's due for it.
When I put a pokemon up for trade on the GTS, and say what I'm looking for, does it automatically do the trade when someone offers what I'm "looking for" or do I decide to accept/decline? Also can I Accept trades for pokemon that I am not "looking for"?
When you put a pokemon up for trade on GTS, someone else must decide to trade for it when they "search" for pokemon. Once they decide to trade for your pokemon, it automatically trades and that's that. You don't get a chance to accept/decline it. They can't offer anything but what you said you're looking for.
While you have a pokemon up for trade, you can ALSO use the "search" to look for other pokemon.
The in-game GTS is a little restrictive, so if you have a complex or flexible trade you want to work out, it's best to do it on the forums/chat here on serebii (or other sites).