How to capture explicit actions from an http request and response packets?

How to capture explicit actions from an http request and response packets?

I am using "tamper data" to look at the http packets. I want to capture
specific fields from these packets and put them in XML. I need to extract
only the fields from the http packets that are generated on explicit
action by the user - for eg. A user clicking on a button or selecting an
option etc. (implicit would be background image etc. that are called with
the explicit action requests by user). I am going through http
documentation but I still can't figure out how to look at an http packet
and say whether it was explicitly asked for or generated implicitly. If
there exists a method to detect these, my work should reduce in plenty.
Thanks in advance.