1) I use a tiny bit of vaseline. Be careful to just keep it on the threads, you don't want it to get on the gluing surface of your neck.
2) You can get away with 10 degrees without string trees. I've never used a locking nut, but I'd think that if you had any break over angle at all and locked the strings you would be fine without trees. Someone please correct me if I'm wrong on that one.
3) Locate your fretboard starting at the nut end by placing the nut where it needs to be in relation to the point of the headstock angle. The nut should sit on the last piece of flat real estate with the HS angle falling away immediately past it. Make your body whatever size it should be. Just figure out which fret you want the neck join to be at. I figure that by leaving just enough room for the neck pick up to clear whatever cutaways and scoops I have planned. Locate that and butt the other end of your fretboard against it.
4) I start with 60, then 100, 150, 220, 320, 400, 600, then micromesh from 1500 to 12000.
SR
Scott has it on the money here apart from the locking nut-string tree thing.
Locking nuts have an angled face that the string is clamped to, The string tree ensures that the string continues away from the back of the nut @ an angle that is similar. If you have no tree there is a possability that the strings will be pinched against the edge of the locking block & snap. So if the headstock is flat (strat like) you will need a tree, but if it is angled similar to the plane of the lock nut you will be fine without one.
Best advice id to just spend a while looking thru the build threads on here. Go download a load of drawings & study them aswell, they will have loads of critical dimensions to guide you. then start experimenting.
Someone posted this site a while ago. I forget who, but it has a massive amount of very good information.
My link
Download all of it for a nice library of referance info. Pain in the ass but this is probobly the best way to get yourself familiar with what you will need to be thinking about to build good guitars.