Deleting DB tables for plugins and subsites that have been deleted

Hi

In my MS install I just realised that there are a large number of database tables for plugins that I have already deleted. In fact there are several tables associated with subsites that I have deleted in the past (I did not expect to have these orphan subsite tables hanging around).

Any suggestions as to how best can I delete these plugin tables and DB tables for deleted subsites. I can do this directly from phpmyadmin, but I dont really know which table belongs to what plugin/subsite.

I am sure there is a simple way to clean the backend database.

Thanks