Never end with Q and A

I think the worst way to end a presentation is by asking, "Now, does anyone have any questions?" 

It's a presenter's responsibility to make sure your audience gets what they came for.  When you take questions at the end, you lose control.  You're not in charge of what's asked.  You're not in charge of whether or not it's relevant to the talk, interesting to the entire audience, or even appropriate.  A questioner may represent the interests of a few people in the audience, but rarely all of them.

More importantly, when you do Q & A at the end, you neglect the most important part of your talk.

Hopefully, you're doing a presentation because you want the audience to do something with the information–to start their applications or consider your college or buy your counseling service.  The end of your presentation should call your audience to action.  It should send a clear message of exactly what it is you want them to do with the new information.  Everything you do in the talk leads to this.  And how you leave them feeling at the end is how you'll leave them feeling about your talk.

Why leave that up to someone else?

It's fine to take a few questions during your talk (stop at appropriate times and let people know how many questions you'll take before you move on).  And maybe let them know you'll answer any additional questions afterwards.

But don't relegate the end to Q & A.  That part of your presentation should be all you.