If it is checked to me in the big blind and I have an unpaired AK hand, should I draw three or four?

This is for 5 card draw btw

How many did the SB draw? How has play been so far? Has anyone bluffed too much? Any prior information matters. I would probably draw three in most situations but it's going to take a pretty amazing draw for you to put any additional money in this pot.

Yea, we need more information here. How many players stayed in? Is it heads up with the small blind?

How does the table play? If they tend to fold easily, this is a great bluffing spot. You could try the standard patting bluff, i.e. raise pre-draw, stand pat, and bet/raise after the draw. Other option would be to toss 1 and bet out after the draw, hoping to represent a made flush or straight draw.

If you're trying to actually make a hand, drawing three gives you the best odds to hit one pair. It also gives the impression you started with a pair, so you might still win with a bluff after the draw if nobody hit 2 pair or better. Drawing 1 basically says "I got nothing" and you just have to hope you hit something to stay in.