Basically, you should not exceed the battery's rated amperage/hour in charging the battery. Therefore, a 700mah battery should be charged at no more than 0.7 amps and will take one hour to fully charge. A 1200mah battery should be charged at 1.2 amps for one hour, etc.

I usually go to the park with several planes and two batteries per plane. I fly early in the morning, so I charge the batteries the night before. If they are LiPo, they don't need to be peaked; if they are NiMh, I throw them on the charger for a quick peak while I am getting dressed, eating breakfast, etc.