Depends how deep into it you want to go. The biggest piece of advice is just practice and experiment on broken junk first before doing anything that really matters. You'll figure it out.
A few more specifics...
1. A temperature-controlled soldering station is INCREDIBLY helpful. I worked for years with just a basic 30w iron, and built a lot of kits with it, but I bought a temp-controlled station about ten years ago and I'll never go back.
2. Use 60/40 or 63/37 rosin core Kester solder, .031" gauge works great for most PC and electronic work.
3. Make the joints clean and physically secure before soldering.
4. Work with a clean, tinned iron tip. I keep a damp sponge and one of those brass brillo-pad-looking tip cleaners on my bench at all times, use them frequently. Drag the hot tip across the sponge, then plunge it into the brass pad a few times, then touch solder to the tip to lightly coat it. When you're done for the session, repeat this and store the iron with the tip coated.
5. To make the actual joint, place the tinned tip so that it touches both pieces to be joined (either two wires, a wire and a lug, or a component lead and a PC board pad), heat the joint for a second or two, then apply the solder with your other hand to the joint opposite the iron. The solder will melt and flow towards the iron. It shouldn't take much solder, and it shouldn't take a lot of time. Remove the solder lead first, then the iron from the joint.
If done properly, the joint should be shiny, and the solder should not "ball up," but rather flow smoothly into and around the joint. Common mistakes are using too low of a heat setting, which actually requires LONGER times to solder and can damage components, and applying the solder to the iron instead of opposite the iron.
It's easy, really. The skill in electronic work comes from learning to DESOLDER stuff without ruining it, especially small traces on boards.
