Prepare as thoroughly as possible so that you can maximize your time with the materials.
When working on papers for classes or conferences, seek out archives, libraries, or research centers that have material pertinent to your subject. Study these collections as much as possible in advance to ensure they are the right fit for your project.
Be extremely clear about your needs for research materials. If possible, know exactly what you want to look at before you arrive, and gather together call numbers and titles of everything you want to look at in advance.
If the archive doesn’t have a complete online catalogue, see if the staff will mail you a hard copy. You may also wish to contact the archivists directly and ask them what the archive has that is related to your topic. Most archivists are more than happy to talk to you and provide assistance identifying useful materials.
Some archives allow you to request materials ahead of time via the Internet, so they are waiting for you when you arrive. Some items may also be kept off site, so the archive may need time (days or weeks) to locate them.
In all cases, when reaching out to the archive directly with questions and/or requests, be sure to do so well in advance of your visit!
Archivists tend to be nice and helpful, but they understandably don't like having to explain the same rules over and over. The better you know the rules going in, the better use you'll make of your limited time.
Know the archive's hours of operation. Some archives stay open later on certain days, which may be beneficial if you are travelling or trying to avoid crowds. Also, some have seasonal closings for holidays, inventory, etc.
As soon as possible, make an appointment to visit the archive. Space may be limited, especially if your visit will require the use of technology (DVD players, audio players, film projectors, computers, etc.)
Make sure you have clear directions to the archive and various travel/transportation options available. (If one form of public transportation breaks down, is there an alternative?)
Budget appropriately for any related expenses your visit will entail (research fees, photocopying fees, etc.)
If the archive is restrictive about copies/photography, be prepared to take notes on-site, as opposed to working at home from copies.
Research food options at or near the archive so that you can find and acquire meals quickly and maximize your time in the archive itself.
Finally, be on the lookout for research grants that provide funding for travel. (There are several here at the GC, and many others outside the CUNY system.) Some archives even have research grants to bring you to their institutions.
As always, be sure to check the archive's rules for what you need to gain access and what items may or may not be permitted in the archive during your visit.
Consider sending a nice thank-you note to the archivists. You may want to go back, and it never hurts to show your appreciation.