If a normal human being can anticipate what kind of content might be found on this page:
…then you can bet that a search engine will be able to figure it out, too. Search engines are just dumb humans. Here is a tip: Write your file and directory names like you were organizing a book. For example, if you were writing a online book about insects (and spiders, in particular), a good, human readable URL might look like this:
A URL that looks like this:
InsectWorld.com/page.asp?cat_id=23&page=15 is bad. Very bad. Crazy bad.
See where I’m going here? If you can read it, so can a search engine.
BTW, don’t over do it. (e.g. don’t make them too long). You should be able to tell a friend what the URL is (out loud, using your own voice) without sounding like a complete idiot.