How to clear space on my iphone?

I have the iPhone 4 8gb. With all the software and stuff that leaves you with 6.2 gbs. When I go to my usage and add up all my apps music pictures etc I'm only using 4.012gb of my 6.2 yet it says I'm using 6.2 what is taking up the extra space?

Well you can delete everything that you don't need. Or maybe a glitch/bug it might be a virus just to let you know.