Question 1. As a librarian with archivist experience, I overthought the whole naming thing when I started out. Eventually, I switched to a simpler system. For the slides I scanned, I just used Accession numbers, then uploaded every scan to Flickr. That works if you don't mind having your photos public, because you can search for photos online.
For the prints I scan, I use archival standard scanning as explained at archives.gov. This drives my relatives crazy because I save them as TIFF files, but eventually I change them to jpgs for sharing, and heck, I can't help myself. If I'm doing all this work, I want them to be scanned to the highest standards. If you don't care about quality, I've heard of people photographing old photographs. It depends on who you are and how much you care; I obviously care way too much, but not as much as I could.
Interestingly, for newspapers, I photograph the original and then try to find a place to give it to because my photos are good enough. I store original articles (the photograph and my transcription) in Google Docs. If I can find a digital version online, I definitely don't keep my original--well, with one or two exceptions.
I never even try to identify who is in a photograph until after I scan it because it's much easier to see after it's scanned. If someone has written on or near the photograph identifying it, I usually scan that and name it the same as the original, adding the word information. Sometimes I do modest photo editing.
For naming, I use a simple system. I label them by the surname of the first person on the left side of the photo. If it's a photo of a bunch of Coulters, I name it COULTER PHOTOGRAPHS, then name the people in the photo. If it's a document, I label it COULTER DOCUMENT, then name the person in the document. I file the originals in an acid-free file folder called "COULTER" and file the scans in a folder on my desktop (backed up online and on an external hard drive). Even though I have several hundred Coulter photos, at this point it's no big deal to sort through them if I ever need to find the original. Eventually, after I've shared all the scans with anyone who might ever want them (and published a book or two), I'll donate the originals to a museum that's climate controlled. I store photos I haven't scanned in acid-free boxes.
If I don't know the people in the photograph, I label it UNKNOWN, post it on Flickr, and email every possible cousin to see if anyone happens to know who it is.
Question 2. Preservation. There's plenty on the Internet that explains how to preserve items, so I'll keep it short. Store letters and other documents unfolded.