First off, are you talking a two person ladder stand or one? If it's a one person, that should be no problem at all. I typically do what HM said above.. that's the easiest, but you have to be careful and have your hands up pretty high when the ladder becomes vertical. Another way I have done it before (and it's time consuming) is to "walk it up". This takes a little more muscle, but for the shorter people out there it's probably easier. Instead of putting the legs on the ground where they will be when the stand is in place, put the "V" of the top of the stand on the tree as high as you can reach. The legs of the stand will be about 15'-20' away from the base of the tree (depending on how tall your ladder stand is). Then strattle (sp?) the ladder and lift with your legs and move the sitting area ("V") of the stand slowly up the tree about a foot at a time. Once the stand begins to get more and more vertical you can begin to set the legs into place where you want them.
Hope this helps!-- and oh yeah... don't do it HM's way on a windy day!!! The way I just described works best for shorter people or windy days.