Actually, you might try opening wide out. f4 or so. This will further reduce your depth of focus and thereby further isolating your subject matter. Also allows faster shutter speeds to further reduce movement. And as Ian suggests, definitely invest in a tripod. If you can find one cheap enough, get one with a reverseable mast so you can mount the camera upside down, closer to the ground and closer to your subject. If you shutter speed gets below 1/125th you will probably also need a shutter release mechanism (cable, remote, et al.). What kind of camera do you have?