+1 for Cumpiano and Natelson, coupled with a LOT of research on internet building forums, with wise temperment splashed in to avoid the "I'm the expert syndrome" from respondants.
Although your post is only 4 questions, its a HUGE post, and you asked VERY open ended questions that can't be answered with that little information.
But, just for kicks, and because I'm in a mood, I'll bite, seriously:
I need to know what tools I need to use
Depends on if you plan on doing everything by hand, or machine. Personally, and this is not all of it: Bandsaw, resaw, table saw, thickness sander, jointer, DA Orbital, Belt sander, router, laminate trimmers, Foredom, Drill Press, compressor, HVLP spray gun, and a whole slew of hand stuff from clamps, X-actos, razor blades, chisels, files, sanding blocks, granite plates, vise, different types of clamps, cam clamps, spring clamps. . . and did I mention clamps?
how thick the wood should be.
Depends on your specs and your plan, what size of `ukulele, what part, what wood, where it is.
I also ned to know what kind of wood to use
Depends on what you're looking for in the instrument. Basically, hardwoods.
how to shape it into the body
Depends on if you want to do it by hand, or use a Fox Bender.
I would also appreciate any information on how to hold everything together.
Depends on what "everything" is. Jigs, clamps and glue is a start.
I would also like to know how to create the fret board.
Depends on if you want to do it by hand, or machine.
BTW - add hand saws to the tools needed (above).
Take this, and Tarhead's response, and do some research. I don't think there's enough posts here to cover what you asked. BUT, do a search for older posts on the topics that you need answered.
Aaron