How to conduct a battery pull?? I'm new to Blackberry.

I know that you have to pull the battery out, but does the phone need to be on of off when pulling it out? Also, do you lose any information (Texts,songs,etc.) when you do a battery pull??

My Bold 9790 is lagging a little when I swipe through photos and scroll through my music list and I was wondering if a battery pull will do the trick. I just got the phone 4 days ago.

Thanks!