Tripods are cheap as chips nowadays, but the cheaper ones have a few flaws. Most importantly, they are too light, and too unstable. So what do you do when you are working on macro stuff, and your tripod won’t stop vibrating, or the high winds are trying to disturb your photographic peace?
Quite simply, most of the time, your tripod will be unstable because of shoddy construction, which can’t really be helped. The downside is that if there’s movement in the legs, you’ll find that the wind can actually move your tripod around slightly.
Normally, this isn’t much of a problem (although if your camera is moving, there’s no point in lugging a tripod around, right?), but if you’re working with macro photography and similar, you might find it a bit cumbersome.
So basically, attach something heavy to the bottom of the tripod, hanging from the bottom rod (the piece that has the tripod head attached to the other end). Some tripods come with hooks attached especially for this purpose, but you can easily make your own with a piece of string, a hook, or something similar.
Alternatively, take a triangular length of fabric, and tie each corner to a leg of the tripod. You now have a hammock in the middle, underneath your camera. Fill it with heavy things (stones, camera lenses, the treasures of the Sierra Madre, whatever you happen to have handy), and your tripod will be firmly pulled to mother earth.
The result is that your tripod is held firmly against the ground, and that your camera is held a lot more steady! Bonus.