I will typically do a search before.
METAR's - I check airports within about 50 miles from the West and North of me (as that typically is the direction weather travels where I live). I'm looking for wind speeds/directions, visibility, cloud heights. If there is a significant difference between the METAR at my home airport as opposed to an airport 50 miles to the west, I take note and will look a little further into the trend, and if I can expect it to get worse or not.
TAFs - Even if I'm just going out to some slam and go's for a couple hours, I always like to look at the TAF. Although it's not science, it will give you a good general trend to expect as the day goes on. It can atleast reveal if things are expected to be stable or unstable. I'm looking for wind shifts, directions, lowering visibility, lowering clouds, etc. If I notice that I'll file that away in the back of my head for note while flying to watch for any possible changing weather.
NOTAMs and TFRs - I can't believe no one has mentioned this one yet! TFRs are very important to check now a days, cause a President (or other entities) can pick up and move into your area with little or no notice. It's your responsibility to know this, and don't rely on hearing this kind of information on the ATIS either. If the Prez decides to show up in your town they'll typcially be a 30 mile TFR around where he's at, and that can get you in big trouble quick (even doing pattern work!).
PIREPs - I like to take a quick glance at PIREPs to see what other pilots are reporting out there right now. Main thing I'm looking for is turbulence reports, or wind shear information.
And thats about it really. Sounds like a lot, but once you get good at doing it, and get comfortable with reading and understanding the reports, this should be a couple minute ordeal, unless the weather is going down the tubes, then you'll need to spend a few more minutes taking in all other available information to make a safe decision. And no need to call FSS for the reports either, just use the available info online.
Remember, your PIC now even if your just in the pattern, so you have a huge responsibility in making all the proper decisions with all the available information you have. Don't take this responsibility lightly!