Is it possible to take decent pictures of yourself?

I have an Nikon D3100, is it possible to have the timer set (on tripod), and have it automatic focus on me while I get in the right position?

I tried it at one point, and the background was ok, but I was blurry in the picture. ANy ideas or solutions to this?

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Place something where you will be posing and focus on that.
Then remove the thing and turn off autofocus.
Start timer and go to your mark.

Since your camera can't use an IR remote control, simply put a mark on the ground (were you'll stand), use a broom, a stick or anything that you can place were you'll be sitting or standing and focus on it, then switch your AF to MF, clean the area, press your shutter speed and position yourself. You can try using a smaller aperture to increase the dof "if you have enough light".