How to take self portraits with timed autofocus on Nikon D3100?

I run an online clothing store and I usually have someone photograph the pictures while I model the products.
Well, I don't have anybody to take them for me anymore. I bought a tripod to take the pictures myself, but I find it very difficult and time-consuming to get the correct position, zoom, exposure, and focus.
What I have been doing is place a chair on the spot where I will be standing and focus on the chair. This is still trial and error. Most of the time, the pictures are not sharp enough.
I order a cheap $4 remote online and turns out this specific camera is not compatible with wireless remotes.
Is there anything else I can try?

Your images sell your product.

Limiting your expense for a remote shutter release to $4 is false economy. Just spend the $20 for the Nikon wireless remote.

http://www.amazon.com/...00007EDZG/

As your business grows, think about hiring a fashion photographer and proper models

The D3100 can't use a wireless IR (infrared) remote. Do not buy a Nikon ML-L3, as it or any other IR remote will not work.

The D3100 requires a WIRED remote, such as the MC-DC2.

http://www.amazon.com/...0049D7FHK/

Unfortunately most wired remotes are fairly short. If you don't want a wired remote to be in the way, or if you can't find one that is long enough, you can by a 3rd party RF (radio frequency) remote - which has a longer distance capability and are generally more reliable than IR remotes.

Here is the one I use:

http://www.amazon.com/...005XFVFRE/

There are cheaper ones that will work, but I have not tried them. Any wireless RF remote compatible with a MC-DC2 should work.

Also, you can also use the built-in remote timer in your camera.

Finally, if you are having problems with focusing, put the lens into manual focus mode, then focus on the chair. With the lens in manual focus, it will not change when you take the photo.

Another possibility is that from the spot where you will be, focus on the tripod. Then switch focus to manual, being certain not to disturb the focus setting or the focal length. Place camera back on the tripod. This works best if your tripod has a quick release plate.