Make sure you get a UPS big enough to power all your equipment, except perhaps the printer. When you hook it up, make sure you don’t plug in more devices than it can handle. UPS’s are rated in VA (Volt-Amps) which is roughly the same thing as watts. If you want to understand the difference, read this paper.

It never hurts to buy an overrated power supply — it just covers you over longer outages and produces smoother power during the outages. Of course larger rated UPSs will cost more. You can save on your UPS by getting a power smart computer and LCD instead of CRT screen which uses less power. You might power your big power-hungry laser printer off the UPS but put a small ink jet on it.