I always cut my own hair. Long layers.
Shag haircut is basically a kind of haircut that features layering of hair. It is in these days. There are a number of types of shag haircut to choose from. You can do them in short layers or long layers. You can see what they are and have a look at them as well from the link below;
I don't think you should try this at home! Even one of those cut rate places would be better, one of those Sam salons or something. A shag by yourself would be very tricky!
Pull all your hair up to the top, middle of your head. Hold it in place with a ponytailer or your hand. Cut off in one place. Don't cut too close to your scalp unless you want short, spikey layers on top. Better to start out just cutting a little off; you can always go shorter. We used to use sharpened hedge clippers to get all the hair cut it one slice. When you let your hair down, it will fall into layers:)