One of the most basic processes in woodworking is to join one piece of wood to another. Whether you do it by hand or by machine, joinery is a skill you need to practice. You could take classes, but if you don't have your own personal master woodworker at your side, watching a video or two on YouTube is a pretty good option.
Check out these three popular videos on joinery:
1. Chisel tips for hand-cut joinery. From Fine Woodworking magazine, a furniture maker's tips for chisel use.
2. Joinery basics. A discussion of traditional techniques without the use of fasteners.
3. Forgotten joinery techniques. For fun, watch as joints described in a1900s book are tested.