Prepare before you go.1. Check footnotes of books that used sources from the archives you plan to visit.
2. Prepare introductory letters from your supervisor, department, and whoever else that may be relevant. Also, keep on hand introductory letters with "blank" addresses, like ones that begin with "Dear Director", in case you stumble onto an archive you did not plan on visiting.
3. Reading and deciphering skills/paleography issues. Depending on which era you are researching, the script might differ from what you're used to; so take some time to get familiar with them.
4. Cultural differences. Some archival cultures are less professional than others. You should consider bringing gifts for the archivists -- not as bribes -- because lots of archivists are underpaid devotees, and a material show of appreciation for their role could go a long way. Dr. Jahn said that for example, on his archival research trips in Russia, he would bring printer toner cartridges for the archive, because he noticed that they didn't always have enough supply of those.
5. Know the rules. Can you bring a camera? Can you photocopy materials in the archives? Do they charge a fee for photography and photocopying services? Check beforehand, not just because you'll have to pay for it (or not), but also to get permission from them if you want to publish the scanned pages or images.
6. Check out the living expenses for the area you'll be visiting.
At the archives.7. Make friends, strike up relationships. With the staff, other researchers, people at the cafeteria. Because they might know shortcuts to things that could help you loads with your time at the archive. Remember that you are not the only scholar there -- talk to the others, mine them for information.
8. Don't be discouraged if you can't decipher everything.
9. Get all the reference information copied accurately -- signature/call number/basic author information/file number.
10. Keep a logbook. Note down what you did in every session: what you ordered, received, copied, etc. Sometimes the sources you gather on a trip may be useless for a current project, but will be useful for future ones. Usually, only about 10 percent of what you find will be used in your final write-up; sometimes you'll read for a week and find nothing.
11. Other things to keep note of: your general impressions of the documents, like: (a) the language, tone, consistency or change over time, (b) perspectives between documents, and (c) is there something obviously missing? Think laterally as you sift through them.
12. Be open to accidental finds. If the shelves are open access, spend some time just looking through them, because something you need might have been accidentally wedged between completely different materials.
13. How to keep record of the materials when you're there? Handwriting vs. typing. Typing might be quicker, but there'll be a risk of digital failure. Copying things down by hand, on the other hand, help information stick to your mind. This is up to every person's preferences, of course.
14. Find a balance between quality and quantity of materials copied and scanned, and of photos taken.
15. For those moments of enlightenment: write down your thoughts at once.
16. If the materials are in a language different from what you'll be writing in, decide on the spot whether it's worth it to transcribe the stuff in its original language (you'll get the nuances of the original expressions), or if meanings (from an immediate, as-you-go-along translation) would be sufficient.
When you're back from the archives.17. When you're finished with your dissertation or publication, give a copy to the (main) archives.
I hope this helps, if you're planning to do archival research; and if not, I hope this tells you a bit of what historians do.