You may wish to visit www.sewing.about.com
website, there is some good basic information there on hand sewing, sewing machines, and free project patterns.
Dressmaking is a skill that can be studied on line or in classes, one-on-one is best if you can. But at the highest level, it is a highly skilled process producing garments that you see on the catwalks of Europe and is learned as an apprenticeship or diploma at that level.
For the home sewer, basic steps are taking body measurments, buying an appropriate commercial pattern (or drafting up a basic pattern yourself), adjusting the pattern to fit, pinning it out onto fabric, cutting out, then assembling the garment (or other item). Traditionally you'd sew a toile or muslin first to finess fit then make the fashion garment.
If you are contemplating learning to sew, I'd highly recommend taking some beginner classes as going it alone without support can be frustrating and end up in nothing wearable. A class where everyone is making the same very simple item is the best way as everyone is following the same steps and makes for productive learning.