Male Headshots
Men's headshots are probably easier to shoot then women's, I suppose because men don't carry around as much societal appearance baggage. When shooting a male headshot, I forget about make-up and even wrinkles (it is character, don't you know) but I will retouch out bags under the eyes.
Men should look 'manly.' Lighting can be harder and more dramatic. I try to bring out cheekbones and the male facial structure, and shoot something that reflects what is handsome in a particular face.
Try to avoid doing anything super 'current' with your hair, like gelling it and then doing that flip thing like the guys from 'Friends.' This invariably ends up looking dated in a few years, much like having a mullet will get you cast in 'Knight Rider: the Musical' and not much else. And then you'll have to redo your headshots with each new haricut, an unecessary expense.
Facial hair is problematic. If you look good in it, that's great, if you don't that isn't. What some guys do is shoot both - we start shooting with the beard, break for a shave, and then shoot a bunch more. If you want a really close shave before your headshot I recommend shaving in the shower (of course, not with a corded electric razor). The same goes for eyeglasses (not the part about shaving in the shower). If you look better in glasses, which some people do (me, for instance) then we shoot you wearing glasses. Sometimes there is a glare problem with glasses, but there is always a way to fix that.
Clothing I think should be simple - ties in headshots for actors headshots really bug me and I think it limits the way a director or a casting agent might envision you. Avoid busy patterns and anything floral. When in doubt about what to wear, pick something out that works with your hair - if you have dark hair something dark, light hair something light, etc. Pay particular attention to the collar area. This says a lot about you, whether the collar is a v-neck, button down, etc., it actually communicates a lot of information that a casting agent will assume to be about your personality (ditto for the hair).
And for god's sake lets pay attention to that posture. Nothing is more unattractive than a slouch. Sit up!