New/Old/All option is just pointer to what list should be refreshed and monitored. Ussualy you should always use New one. For now there is nothing to prevent downloading more then once if the filter matches new nzb.
*desperate*housewives* will match any name that has word desperate and word housewives in it.
desperate*housewives* will match any name that STARTS with desperate and has housewives word in it.
desperate.housewives* will match any name that STARTS with 'desperate.housewives'
Desperate.Housewives will match only 'desperate.housewives' name. ONLY that, nothing more, nothing less.
Filters are not case sensitive so it doesn't matter if you write *desperate* or *Desperate*.
Here is an example that will download hdtv version of DHs but will reject all other larger versions:
*desperate*housewives* | A
*hr.hdtv* | D
*720* | D