If it's any guide, here's what I did this past birthday, which I decided to take off.

Wake up whenever
Make a nice breakfast (pancakes, eggs and bacon, coffee on the side)
Relax, watch garbage TV
Go hit some golf balls at the range
Relax some more
Beers
Play some chrono cross
Have parents and gf come over
Beers
Get pizza
Open gifts
Beers
Cake
Netflix and chill with the gf
Sleep