Aside from the obvious living requirements, fill a bookbag with pens, pencils, hilighters, sharpies, a notebook, calculator, ruler, memo pad, post its, and folders to organize your paperwork. one of the hardest things that I found during and after my training was organization.
Memo pad i use to write down trip info's and po requests to make sure i get everything back on payday. Post its i stick to the dash with directions, fuel stops (im assigned to fuel stops as a company driver), and quick reference to remind myself of things when im stopped. For the folders, i actually have a expandable file binder type thing that i bought at walmart for $10 - i keep blank stuff in there like comchecks, scanning sheets, lumper receipts, and paperwork in there. i have a separate 3 ring binder with hole punch for scanned logs. Also bring some paperclips to keep your paperwork together and sorted.
Just my $0.02