Best way to ask a club to dj

Use the search function, quite a few posts have been made on this subject of how to find gigs.

In general, just asking your contacts “what does one do to have a shot at DJ-ing here?” will get you a lot of information and perhaps offers for help. Clearly it helps to have a mixtape handy if you get asked for one, just be sure it’s a good one and done as professionally as possible. The Digital DJ Tips Mixtape course is a very good help there, btw.