For my solder joints I use:
.08 mm 60/40 Rosin core solder
15 watt soldering iron
small heat shrink tubing
I start by stripping the wire back about 1/4 in. and apply solder to each end, this is called "tinning".
Join the two parts to be soldered in a lap style of joint and apply heat. Hold the iron on the joint only long enough for the solder to melt and then remove the iron.
Soldering with too much heat can damage components such as modules, LED's etc.
I also use my"helping hands" to hold parts while soldering, depends what I'm soldering.
I have a small tip on my heat gun which works pretty good, there again, in and out quickly. The side of the soldering iron works in small places.
Practice, practice, practice. Soon you will be a pro
Mel