Soldering is an art that only gets better with experience.

Make sure you have atleast rosin core solder, an iron that gets hot enough (40W or more), and a number of different sized tips depending on the soldering job.

When soldering heavy gauge wiring or round cell packs you will want to use a thick solder tip. Smaller jobs are easier with a smaller tip. If your tip is too small for the job, heat will not sink to the object being soldered fast enough. The result is that you will have to hold the iron on the object for a long time causing everything to heat up excessively. This is often a bad thing.

I bought some aluminium flux a while ago to solder Lipo packs and I've since found that the same flux works wonderfully on all soldering jobs. It makes soldering to anything very very easy. Chrome, nickel, aluminium, etc. I highly recommend getting some even if you're not soldering aluminium.