In D3 you don't assign points in the skills like in D2 you simply unlock them as you level up. By default the skills go in certain button slots on your UI, but you can go into settings and check the Elective mode to put whatever skills onto whatever keybinds you want. So far there is only 1 "spec" which is really only a set of skills you choose. Personally I'd love to see dual skills sets, similar to dual spec, but just have to different set ups you can go back and forth...say a defensive set up and an offensive setup.
When you get to 60, you unlock all the skill. From there you can switch the skills around anyway you like. Most of your stats, well 99%, comes from your gear. So you must gear up to get better. You can re-roll with a different class (there are 5 total) if you want to try out other skills. There is no point in re-rolling the same class.