If the table saw has been properly stored, you may not have to do much before you can start using it. Find out if there's a reason why it hasn't been used other than a loss of interest or lack of time--for example, maybe it needed the bearings replaced and your friend just never got around to it.
Has it been subjected to the elements?
If it has been subjected to the elements, you may have to deal with rust removal and the motor could be damaged, in addition to any other issues it might have had otherwise.
If it was stored in a non-climate-controlled garage, the table could still have surface rust but should clean up fine. There are many ways to remove surface rust, from WD-40 and steel wool, to sanding, to rust-removal chemicals.
Check the owner's manual
The owner's manual should be your first resource. Read through it so you know how to properly disassemble and reassemble the saw. The assembly instructions will also include some information on how to calibrate the fence, at the very least. If your friend does not have the owner's manual, you may be able to download it from the saw manufacturer's website. Failing that, check vintagemachinery.org or owwm.org.
Before you take it home
- If the saw is currently fully-assembled and it worked fine the last time your friend used it, test it before you disassemble it for transport.
- Check that the saw includes a riving knife/splitter, blade guard, fence, other accessories (like a miter gauge), and any wrenches necessary for making adjustments or swapping the blade. Familiarize yourself with how to use them correctly. This may include reviewing the manual.
- Align the blade parallel to the miter slots
- Align the fence parallel to blade and miter slots
- Check that the belt from the motor to the arbor is in good condition and not rubbing on anything
A riving knife is safer than a splitter
If the saw is old enough to have a splitter instead of a riving knife, it will have a greater chance of producing kickback. Although a splitter and riving knife both prevent the blade from being pinched, a splitter is always positioned at the same height, while a riving knife raises and lowers with the blade. This allows the riving knife to maintain a constant distance from the back of the blade. This means that when the blade is lowered for a shallow cut, there is a huge gap between the back of the blade and the splitter, as illustrated in a kickback incident analyzed on LumberJocks. A splitter only performs as well as a riving knife when the blade is raised to full height--which itself is considered unsafe unless you need the full height of the blade to make a cut.
Aftermarket riving knives are available for some saws, and you should consider getting one if your saw comes with a splitter.