I jailbroke my iphone 3g?

I jailbroke my Iphone 3g and I wanted to know the things that I shouldnt do so as not to get caught by itunes? applications I shouldnt open and from where I should download applications? can I use safari as normal? and the Installous application isnt downloading anything.. and they asked me about the itunes account.. is that normal? and everytime I download ebuddy or anyother application.. I find myself transfered to the App store :S.. what to do? and what applications and things shouldnt I open or use?