For both hair on the head as well as facial hair, I think it truly depends on the individual guy. What works for one person's face may look terrible on another.
That being said, overall I'd prefer that my guy didn't have a full beard - anything else, I'm indifferent. If a guy can look good with longer hair (shoulder-ish length) then he should try it. I'd like to have something to play with. haha
That really depends on what the guy does with what he has.
If his hair is thinning, then most of the time I think it would be better to cut it REALLY short or shave it off. Girls are not fooled. You can grow your hair as long as you like, but if its thinning on top we notice!
Bald men can be hot - especially shaved ones.
I don't mind facial hair, but wouldn't get attracted at first site to a man with a full beard. If you have one then make sure it is clean and well kept.
In the end it depends on what makes you feel good. If you like having a beard, then you should find a woman that can appreciate it also.