U might can tickle yourself, but i don't think you can tickle torture yourself, or laughing for real because of your tickling.
If you want to feel some tickling sensation to have fantasy that someone is tickling you, you can follow isabeau's advice e.g.you could lay down on your bed and having your hand slowly or quickly tickling your feet, without watching it and try to convince yourself that truly another person is tickling you. Maybe creating a scenario to get you in the right mood will help.
Another idea that comes to my mind.. it might be stupid, but anyway... maybe you can go to the shower, put the water to run on high pressure, and put your feet below. Don't look at them, look from the other side. Imagine and try to convince yourself that this small tickling you feel is not from the water but from some feather/finger/electric toothbrush that someone uses to tickle torture you, and that you are really ticklish and helpless and you undoubtly can't hold yourself and you feel the tickling so much that you are going to laugh hysterically. Move your feet a little, as the imaginary feather runs across your soles to your toes. Maybe you end up feeling a strong tickling sensation.
I hope i helped a bit.