When I first started quilting, I did a mixture of a lot of the above advice
I started with a pattern that required not too many colors (up to 5). I would pick a main fabric, usually multi-colored that I loved and would build around that. In the beginning I also used to pick colors from the same line...the matching is done for you! I used to be so paranoid about getting the colors just right...until a quilting teacher once told me: "Why do you always worry about not matching the colors. You dress nicely so you have a good sense of colors; just go with your instinct and have fun with it!" So don't worry, it will get easier as you go along. Now I rarely pick from the same line and love to throw in some zinger fabrics like a black and white or a funky print. I also don't necessarily have a pattern in mind and love to make up my own thing. Now picking colors and fabrics for my projects is my favorite part