It’s been an unusually busy start to 2012 for San Francisco real estate. I haven’t seen this active a market in the January-February timeframe in a few years, and many other agents with whom I’ve talked agree.

There are currently 183 single-family homes, 243 condos, 33 TICs and 53 two- to four-unit buildings in contract. Many well-priced properties are being snapped up within a few days or a week’s time. This means that when I head to a home that’s listed on the Tuesday broker tour, I’m often informed shortly after crossing the threshold that the property is already in contract.

For buyers, this means that getting to that first open house is critical if you want the opportunity to make an offer. Many times, the first showing of a home is at the weekend open house. And a side note: Though an agent enters a listing into the MLS the week prior, the property may not be quite ready for showtime. Sellers sometimes still need to clean out the garage or complete final de-cluttering. It never hurts to have your buyer agent request a showing prior to the open house, but don’t be surprised if the sellers request that you simply attend the open house.

If you’re on the home-buying warpath, I recommend being fully preapproved with a lender before you seriously begin looking at houses. There’s nothing worse than stopping in at a Sunday open for a lovely 3BR house in Noe Valley and learning that they’re taking offers in three days—and you haven’t even submitted any financial documentation to a lender yet. Believe me, there are enough property details to review in order to determine whether this is the house for you (i.e., disclosures, comps, neighborhood info). Adding a quickie preapproval that doesn’t give you time to consider what you’re getting into is not the best way to proceed.

Based on the high volume of homes going into contract—and the likely possibility that Spring will usher in even more inventory—it’s clear that more and more buyers are getting off the 2011 real estate-buying fence and making purchasing decisions. I don’t expect this activity to soften as the months wear on, due primarily to the low interest rates and feeling that we have definitely reached the bottom of the San Francisco market in most neighborhoods.

The two-unit building above at 208-210 Caselli in Eureka Valley is the latest property in San Francisco target by a multitude of serious buyers in San Francisco. Vacant and featuring two 3BR/2BA units with wood-burning fireplaces, open floor plans and hardwood floors (plus two separate garages), Caselli was listed for $1,399,000 on February 9th. The sellers received 14 offers all over the asking price yesterday (on a holiday, no less).

And Caselli is not the only example of a multiple-offer magnet. There was 1462 11th Avenue, a 2BR/1BA single-family house with an okay bonus room on the garage level that was listed at $649,000. The home  is being sold via court confirmation, which means the accepted offer will be subject to an overbid in court. However, that scenario did not deter the eight buyers who made offers. The winning offer? Somewhere in the neighborhood of $820,000, with a first overbid of $862,550. Another example was over at 119 Joost in Sunnyside, a 3BR/1BA single-family home within walking distance to downtown Glen Park. Listed at $689,000, the sellers received about ten offers and the selling price is reportedly well above $700,000.

To be sure, buyers aren’t flocking to just any property in any neighborhood in the city. Making the cut are typically vacant two-unit buildings or single-family homes in central locations near public transportation, restaurants, services and cafes. Particularly popular are areas like Noe Valley (see the recent SF Chronicle article about my ‘hood here); Mission Dolores; Eureka Valley; prime parts of Bernal Heights; the Inner Sunset/Richmond; and Sunnyside.

What’s fueling this sudden urgency among buyers? For one thing, the low interest rates are convincing people that they can lock in a favorable fixed rate and put their mortgage payments on auto pilot. I also think the reality is setting in that prices are not plummeting in the near future, and that we may have hit our low point in the more popular neighborhoods. Get in now before prices go up any higher, the thinking is likely going.

I do have one piece of advice for buyers: Use the list price as a mere reference point. For example, if the average value for a 2BR house in your favorite neighborhood is $800,000 and a great home comes on the market listed at $695,000, chances are good that the house will sell for significantly more than asking.