Head Porting Help

I want to do some basic porting on my recently acquired 302 heads that are going on my 318. I've never done any porting work before, but I want to do it to these heads. Motor has Edelbrock Performer and Spitfire headers. Can anyone give me any good advise on basic porting work. I'm not looking to go crazy, just want to enhance street performance the best I can with what I have. Any tips or advise is appreciated. Thanks Mike