How to clean up other on my iphone 4?

Well i checked on itunes today to check total memory used, come to find that my Other is taking up 2.52 gb. How do I clean that up so its not using so much space? I delete emails lots, messages, but nothing. What is everything that falls into the "other" category? I wanna erase some of it so i have more storage

The phone needs some to use for itself, you should unload your videos and photos to your PC as you don't need to keep everything on the phone.