Interesting answers above, with witch I agree (50' for a 1hander). Much beyond that point (moving water) you may have to do a lot of mending in the early part of the cast.
Actually accurate (distance casting) is fairly easy with a 2hander. Once you've got the line stripped off it becomes a question of aiming where you want the fly to land. A lot of that has to do with anchor placement .... practice, practice, practice!