What is fasting?
Should I do it?
Yes, if God's calling you to do so! Fasting has been used in many cases within the Bible. Normally it was a ritual done when people were repenting over something large and were humbling themselves, or if there was something 'very' important that they were praying for. It can also be a wonderful way to bring yourself closer to God, because it clears the mind of some distractions (Food can often slow the thought process down).
As for the level of fasting, that's a personal desicion. You can go on a total food fast (although I'd suggest water, however go by what the spirit guides you). You can go with a selective food fast - Fasting from certain foods and only having the most basic and maybe not so pleasurable ones. Or maybe a fruit fast. The options are endless! If I remember correctly, 3 days is the most extreme of a fast..but you could do it even for just an afternoon or something. Just pray about it, and dedicate that time to God.
Or, as the person above suggested..you could fast from an activity too.
Fasting was something that was even important to Jesus, as he mentions it several times. I could post you endless verses from throughout the Bible..but to be honest, I would just suggest going to an online Bible and typing the word "fast" into the search. It'll come up with tons.
There's a sermon I particularily liked that regards this subject that I would 'highly' recommend to you. It's an hour long, and you can listen online or download it. (Safe site, too). It covers the Biblical importance of fasting, the different benefits, and different kinds. I learned so much!
You can find it here:
http://www.amazingfacts.org/media/everlasting_gospel.asp
Just scroll down a bit, it's 18th or 19th on the list and called "When We Fast".

I hope it's of some help, it answered all of my questions for sure.
Blessings and Love,
Sarah