I'm not sure what your level of expertise is, but it's important to note that footings and piers are two different things (no offense intended).
Usually for a deck piers will suffice on their own, provided they are wide enough (typically 12" is good) and deep enough to go below the frostline in your area (3 ft deep is a good rule of thumb). The main reason you would use either footing/pier combination, or a 'belled' pier (a wider base underground) is if you'll have a roof on the deck, to protect from uplift in strong winds.
If you're actually using both footings and piers, rebar would be suggested to tie them together since you'll have a 'cold seam'; that is, you'll be dealing with two separate pieces of concrete instead of a single one.
Usually your main rebar would have a 90 degree bend near the bottom, and be fully encased in concrete, as the concrete protects the metal from moisture. You can either suspend it after the first few inches are poured, or put a couple of shorter lengths into the ground to support it while the footer dries.
Again, if you're simply pouring piers, I wouldn't worry about rebar. As long as you're below the frostline, you will be fine.