What do I need to ensure my presentation will go smoothly? From a technical stand point, what do I need to show up to a conference with (in general) to ensure that my presentation will go smoothly?

Two things I can think of:


Presentation remote 
Equipment to connect my laptop to the projector


The remote is simple enough, it just needs to work with my computer and be reliable. Connecting my computer to the projector is not trivial since a lot of laptops don't come with DVI or VGA output any more (mine doesn't!). What kind of output do I usually need, DVI or VGA? Do I need something like this which supports all output methods (seems like over kill but might be a good investment)?

Is there anything else to make sure I am prepared to deal with the technical aspects of a presentation?
From less esoteric to more (I've seen all these things happen):


Make sure you know how to "send the image to a projector". Not all laptops do this automatically, and I'm surprised at how many people don't know how to do it. I've also seen people be confused by the mirroring feature on Macs.
Verify that there's a power outlet or some place to plug in your laptop. Driving a projector eats power, and you don't want to drain your battery during the presentation
Turn off screen savers. at the very least it's annoying, and sometimes the screen saver does wonky things to the projector display.
Turn off your notifications (mail, facebook, twitter, skype...). It's amusing for an audience (but not for you) if during a job talk they all get to see a subject header of the form "Interview at University X" where X is not where you're at :)
Make sure you have the right display converters. Usually something that converts your laptop to a VGA is standard. Macs are particularly difficult in this regard. 
Watch out for resolution issues. Most laptops are smart enough to drop resolution to deal with a projector, but sometimes they're not. 
Keep a backup copy of the slides in a portable format (PDF or PPT) on a usb stick. In the worst-case you can always borrow a laptop (from the previous speaker even) and load up the slides. Dropbox/a web page is ok but not great because it requires an internet connection. 


And above all, as David M. R. says, check the setup beforehand if you can. Even that doesn't guarantee a smooth presentation, but it eliminates a lot of the potential problems listed above.