Boat slip question

Question for the group please: I have leased a boat slip in New
Jersey's largest lake, size is 21' X 8'. I have never used one before.
What is the ideal width of the boat (I don't have that yet) that I
need to fit into the slip space and still have comfortable room for
folks to get in and out of the boat and of course, to protect the boat
properly. And, secondly, what is the best way to secure the boat. The
slip has no protective tires and I'm wondering what kind of lines to
use and how many. Thanks. Jack.