How do I approach new water stains on my ceiling?
I have had several calls since Irene for similar problems on roofs that had previously had no leaks.  As most have already said, the first step is to get up in the attic for a visual inspection.  I would remove the insulation over the stained area to check for damp insulation and allow the ceiling drywall to dry completely.  Look straight up over the stain area on rafters or trussed for any signs of water staining.  You may get lucky and be able to trace a stain trail to the source of the leak. It is not uncommon that in a storm with wind driven rain for water to be forced uphill into a ridge vent, then track down a framing member. If this is the case, it was an isolated incident and no repair may be needed.  However if the winds lifted a few shingles or damaged the seals around vent pipes etc., some simple repairs may solve the problem.

A word of caution, if you call in a professional roofer, get more than one opinion.  It is very common in that trade to try to up sell uninformed home owners on a whole new roof at around $350 per 100 sq foot, rather than just offer a simple inexpensive repair. I would try to find a reputable general contractor in your area that will work with you as you learn more about home ownership and give you expert advise and recommend reputable tradesmen for roofing, plumbing, electrical etc., as needed. The best way to find such a resource is by referral from other homeowners or friends. Rarely will a really good GC advertise, as they are too busy already and get plenty of work from referrals from their customer base. Sometimes you can chat with a project pro at a local building materials center, even a Home Depot or Lowes and they may give up the names of a couple of good, well respected home maintenance general contractors.