You might want to take a look at the videos for circular knitting on this page. There are a variety of methods, for large diameter (something like the body of a sweater) and small diameter (something like a sock, mitten, or sleeve).
The process of making the knit and purl stitches is the same with circular needles as it is with straight needles. The big difference is that you are knitting around and around, never turning your work to the 'wrong side'. Therefore every row is a right side row. You also might be interested to know that knitting every stitch of every round, when working circularly, produces stockinette stitch, whereas on straight needles you have to knit one row, purl one row, etc., in order to produce stockinette. So in the round, it's a nice treat for those of us who are not so fond of purling!
As for brand of circular needles, a lot of us here have interchangeable sets where the kit has cables and needle tips seperate and you can use any of the needle sizes with any of the cable lengths. You can find discussion at great length in this thread.