Getting familiar with the venue, looking at your slides on the "big screen" and paying a quick visit to the mirror before your talk help reduce anxiety and stress among other things.
Check the room. One good to reduce the anxiety before given a presentation is to visit the room or lecture hall where your talk takes places before it takes place. This has several advantages. First, visiting the room prior to your talk will show you the way to get there. Doing this you will have answered the question "How do I get to that room?" reducing uncertainty and stress. Second, getting familiar with the unknown room will also reduce anxiety. So take some minutes, walk the stage, look at the empty sits, and make yourself familiar with the place. Third, deciding where is the best place to stand and how loud or soft you should talk will make you look more in control (because now you are more in control) giving you confidence. Bring someone along and ask him/her to stand on the back of the room and make a sound check. The human body absords sound, so your voice will be heard softer when people come in to hear you.
Check your slides. In most conferences organizers will ask you to copy your presentation into their laptop. Try to do it one session before your talk, or even better one day before. Ask if you can project your slides on the screen and see how they look. Most likely the colors you chosen on your computer screen won't be the same on the projection canvas. Or even worse, their version of Powerpoint can mess up your layout and/or font. One quick fix is to export your presentation deck as a pdf file.
Check yourself on the mirror. Is your shirt dirty? Do you have food-rests on your teeth? Does your hair make you look like a mad scientist? If you do, chances are your audience will focus on those things instead of your talk. To avoid that, check yourself on the mirror right before you hit the stage.