However if I make it to specific then I might miss out on things that people just put in general categories.
Several, several years ago - by chance - I happened across and won an auction titled something to the effect of "Wacky Packages - everything but the kitchen sink." This was a random assortment of cards if there ever was one: PSAs, autographs, Ludlows - you name it. A rather nice and intriguing find.
I would follow Paul Maul's suggestion and narrow your search if you are searching for something in particular. Every now and again, however, do a broader sweep if you have the time. True, you'll probably happen across the same old same old, but you'll never know what other goodies you might find.
Sometimes if you are too specific, though, you might only find one or two auctions. Case in point, I was recently searching for an additional "Bum Beans" title to make up what I thought would be the ideal Thanksgiving set if Topps had ever released such. I typed in "Wacky Packages Original 10th Series Bum Beans 1974" and found very little. When I began to delete certain words from my search, however, more choices revealed themselves. A lot of it has more to do with how the seller lists their auction, too, as strictly opposed to eBay's search engine. It is advantageous to a seller to post the maximum number of words as permitted in their description so their auction has a wider radius. However this also increases the number of auctions you must weed through in your own personal search.
Even if you take advantage of the different sort options, I'm afraid the whole thing is "damned if you do, damned if you don't." Too narrow a search, and you might miss out. To wide a search, and you spend half you time rifling through auctions you've seen a hundred times before. Again, a lot depends upon the seller and how they choose to list their auction. They might decide to label it "Pre 77" - but then again, they may not in order to garner as many views as possible by eliminating as many restrictions as possible. And, like Brian Mc stated, the seller might simply screw up.
As far as eBay goes, they want you to see as many auctions as possible, and I doubt they are going to change the way their system is configured any time soon. On several occasions, I have spoken to telephone representatives about the possible option of enabling the user to set additional parameters based upon personal preferences, rather than predetermined eBay preferences. For example, I often open up my computer to find that risque calendar images have been posted in the section labeled "People who shopped for this item also looked at..." I, myself, did not search these out. Nor do I need to open up my computer in my classroom and have these images jump off the screen into the eyes of my 2nd - 5th grade students. ("Family Life," as they call it, is not part of my curriculum!) Even if these images could be blocked, it would all depend upon the words that the seller used, not the image itself. (And speaking to a representative on the phone is like pissing in the wind. One gets absolutely nowhere at all, save to find oneself in a state of aggravation.)
Good luck in all of our searches!