Advice: GET vs. POST vs. SESSION

I was hoping that some of you would be able to give me some advice. I have started creating a web application that makes heavy use of URL GET variables in order to solve a problem that I have had with POST in the past - namely, having to refresh the document and repost the variables when you use the browser's back button. So I enthusiastically have embraced GET variables, but am now having a struggle editing the URL variable string. So this is my question: is using URL GET variables that best way to avoid that browser back button effect? I have thought about using session variable extensively, but that I am going to have to be unsetting them all over the place. So - anyone have any advice? Thanks in advance!