SOLDER ON

I‘m thinking about handling my own guitar maintenance and, in particular, getting stuck into some soldering. I want to try some pickup swaps but don’t fancy paying someone to do the job each time I get the itch for a new sound. What are the key tips that I need to know before I get involved in this? I have a 40-watt soldering iron and a roll of solder at the ready. Now what? D Menzies, via email