I use a 12V battery for charging. I've even hooked to my car battery when nothing else was available. I have an Astro Flite 109 Li-Poly Charger and it was the best investment I've made since going to Li-Poly. It never screws up, Only I did on a couple of occasions.

Li-Poly must be charged at 1C or lower.

Charging at a higher rate can cause them to overheat and burst into flames at over 1500 degrees. Li-Poly should never be allowed to go above 170 Degrees Farenheit. Keep them cool at all times, and be sure that you have more MAH than your plane needs to fly. If your plane is drawing too much Current and the batteries are getting hot, you stand a chance of them catching on fire.

To be safe I always go a bit below 1C (C being the MAH of the pack) when charging. For example a 1200 MAH PAck I would charge at about 1.0 to 1.1 AMPs. This is a form of insurance. Takes a bit longer to get a full charge, but the time is insurance.

Also, never leave the batteries while they are charging, and never charge in your plane. Some even go as far as to charge in a Ceramic pot of some kind.

Also never leave the batteries hooked up if you aren't ready to fly. The ESC typically is drawing from the pack and eventually will destroy the battery by taking it too low in voltage. Li-Po Batteries cannot be discharged below 3V per cell or they are ruined. So if you have a 3S pack, it should never be taken below 9V. A 2S Pack never below 6V. Most ESCs for Li-Poly have this cutoff built in or in the more expensive ones, it is programmable.

Most of this information is sent in the instructions and warnings when you purchase the packs. I've been using them for over a year now, and have only had incidents when I, the operator screwed up. Learn the characteristics, and you won't have any problems.