I've cut my own hair for a while now and most people are shocked when they find out (yeah, yeah). I've been doing hair for close to 10 years now though. Basically, use buzzers, start longer than you want it to be. You can always cut more if it's too long, if it's too short you can't make it magically go back. Use a hand mirror for the back or if you're like me and constantly use one, use your off-hand flat against the back of your neck as a guide.