Summarize this article:

About 5 or 6 inches (12.7 or 15.2 cm) is a pretty good size - big enough to get stuck into the knitting, and quick enough that your blanket will start to look interesting quickly!  Each time you finish a row, attach it to the previous row. Eventually you can stop, when your blanket is as long as you'd like it to be.
Choose the size of the patches. Choose the size of the blanket, and work out how many squares wide it will be. Keep going!