At first thought you'd might be incline to think "oh, another list of para diddles to drive everyone crazy while I warm up". And while that is certainly an important step in a playing situation it's not it. Do your dishes. That's right, fill the sink with how water and do a load of dishes! 10 to 15 minutes in the hot, soapy water will totally loosen you up for your rudiments and playing. Works every time guaranteed. Now, an important point, don't wear rubber gloves! It's not nearly as effective if you do.
While this is a great way to warm up at home, obviously you're not going to roaming the neighborhood at a gig looking for some one's dishes to do. Fill the sink in the men's room with hot water and immerse your hands, again for as long as you feel the need. You might make it a point of keeping a couple of universal sink plugs in your gig bag for this purpose.
Keep in mind that just keeping your hands in running water will not do the trick either. Nor, is placing them over heaters, radiators and similar heat sources.
One final note. After getting them nice and loose from this trick put on a pair of light gloves (or your drumming gloves) to retain the heat. They will chill down if there's too long a wait before playing.