I don't know if the Heathkit company as still around or not but they used to sell a simple soldering training kit. Just search the internet and I'm sure you can find a lot of pics showing what a good solder joint looks like. Basically it's shiny, doesn't "glob" up, conforms and flows to/through the joint. Get out out some wire, an iron (yes, I said iron, not gun), and some small diameter solder and it'll all come back. Add to this some heat-shrink tubing and you are well on your way to making 100% solid reliable electrical connections.
Hint: Very important to keep the tip clean and tinned, put a little solder on the tip to help transfer the heat to wire/joint, hold under the wire/joint, and apply solder to the top side of the wire/joint. The solder will wick into the wire/joint toward the heat source.