D/L'ng headers is the base way, if your newsreader can 'filter' the results (i.e., get nfo, nzb, ect. type files) that will improve the result, Newzbin in at the top of the indexing sites, cost is around 25cents/US per week, but many sites (including this one, IMHO) do a fair job of listing as well, including many that (believe it or not!) that Newzbin 'misses'. I think a lot of the 'editors' there are a bit lazy, then again, they are 'paid' in free access, so the result is a bit variable at times.
There are many sites (and newsreaders) that will generate nzb files as well, if you have the posted basic name of the file. Even if the nzb is posted here, I'll simply grab the filename and do a search myself, letting the newsreader generate the nzb, or go to one of those nzb sites.
But again, over the years (9+ years going on with usenet binaries), I've learned to keep a good eye on several groups with header d/l's every day or so. There are ways to get it faster (Giganews has been testing a 'turbo' header system) but you need to narrow your groups you're interesting in and concentrate your 'deep search' that way. I 'watch' about 10 groups that way, takes about 20min/day worth of (computer) time to get them. Worth it, as at least 3-4 times a week I trip across something I like, that arn't listed either here or on sites like Newzbin. But that's just me.