Most pizza parlors have little need for excessively large tables, since customers come in groups of four to six. For that reason, you should only need tables that are three or four feet in length (or diameter, if you want a round table). Tables that are this size allow you to maximize your available dining space and accommodate as many small groups of people as you can. Of course, you may occasionally have a few large parties come in. In order to seat all of these people, you can simply squeeze a few of the tables together. You may also want to encourage customers to call ahead if they are going to have a lot of guests, so you can prepare ahead of time and decrease the wait.