The first things to do:
Run aptitude interactively (no command args)
Select options, tell it not to include recommends.
Then, go down the list of all packages and if its one that you
yourself don't specifically want installed, then mark it as
automatic. Continue going down the list. When you think you
have it all good:
hit 'g' to see what aptitude would like to do.
If its wrong, fix it (marking things manuall, install,
whatever), then it 'q' to go back to the main screen. Then hit
'g' to see if its correct.
When everything in the first 'g' screen is correct, hit 'g'
again and it will clean out any cruft build-up you have.
Then you can continue to use aptitude as your package manager
and it will keep the system tidy.
Doug.