Level them up, Use items on them like Protein, Full Restore, Iron, Carbos, Hp up, Calcium, PP up, Zinc, have them hold soothe bell in battle.
you have to take it around with you and let it battle. you cant let it faint to much or just give it the exp share.
Yes you can trade leafgreen version Pokemon to another leafgreen version.
It's usually very hard to have a Crobat that isn't already really friendly towards you in Pokemon LeafGreen. This is because to even have a Crobat you need to level up a Golbat that is really friendly towards you. To make a Pokemon more friendly you simply need to keep it in your team for a while. You can also take the Pokemon to Daisy Oak in Pallet Town to give it a massage.
all you have to do is battle people
you cant... yet
No. Poke'mon Master
defeat it
Not in Pokemon leafgreen only in Pokemon Firered never ever in Pokemon leafgreen And in Pokemon firered it is rare in power plant not available in Pokemon leafgreen?
luxuray ball
you battle with it or put exp. share and battle with a different Pokemon
A ditto with (any Pokemon you put in the day care accept for legendaries)
shoot him with a railgun