For starters, there's a good tutorial on this here:
ruTorrent - RSS Filters
For your specific case, you probably want to use an exclude filter that filters out words that are commonly used to describe full seasons, packs, etc in torrent filenames. So, for example, let's say you want to download episodes of House season 8. You would probably write an
include filter (to put in the "Filter" field of rutorrent's RSS Manager) like this:
/House.S08E*/i
That matches torrent filenames starting with "House.S08E", which by itself will probably eliminate full-season downloads. But then, to be safe, you would want an
exclude filter (to put in the "Exclude" field of RSS Manager) like this:
/( .*DVDR$|.*.Pack$|Complete)/i
This will (usually) filter out DVD rips, packs, and complete seasons. You can filter out additional keywords by adding them inside the parentheses, separating them by a pipe. For example, if you don't want XviD-encoded episodes, you could modify that filter like this:
/( .*DVDR$|.*.Pack$|Complete|XviD)/i
Hope this is helpful!