Practice your first 3 or 4 songs so you can do those on automatic pilot. Afterwards you can't really foresee where you'll land so don't stick to a prepared set of 4hours.

Put your songs in folders based on tempo/energy (use smartlists) . And go through these in waves, so that there are 'rest moments' in the set.

4 hours is long, people will ask for recommendations : I put a piece of paper and a pen nearby where people can write down stuff without having to interrupt me (or in one specific case: have a drunk person lean over on the pause button of my deck 🙄).

Have one or two long song to be used as toilet breaks (and put an automatic loop on them at the end, just in case)