Do you know anything about the library you'll be visiting? Do they have a genealogy section, an obituary index, etc.? If you can't find those answers on the library's website, I'd ask those questions on a message board for the city you'll be visiting. You can get some valuable tips from people familiar with the particular library, tips that could save you a lot of time.

That's the only library search advice I have. I also suggest that you search Find a Grave to see if the burial site of anyone you're researching is listed.

Good luck!