whats the best way to install them...any tips or tricks??
Keep the door in the frame, then hang it? or is it easier to take the door off first?

I put one in yesterday and had a heck of a time getting it to fit properly, just would like to know if I'm forgetting something.

 

Some guys will put the casing onto one side of the jamb, then use that like a nailing fin. I prefer to use a healthy amount of shims to secure the jamb instead.

I leave the door in when I install prehungs. One shortcut I use is to insert some shims around the perimeter of the door to maintain the proper "gap" around the outside edge of the door. You check the floor to ensure it's level, and if it's not you can either shim 1 leg up, or cut 1 leg shorter. I also use a 6' level to ensure both jambs are perfectly straight (not bowed at all, like wimpy jambs like to do) and also I try to make the door as plumb as possible, even if the wall isn't. Check each side to ensure it isn't racked, and as you close the door, check to see if the reveal is straight as the door comes close to latching.

 

Thanks for the reply, XSleeper. I've never had much luck installing doors, but I'd better get used to it, as I have a least a half dozen more I need to put in!
I don'' know what it is about them, I just need one of those office max easy buttons.