Seth, I was always a fan of Bruno Furst’s booklet series You can Remember! A Home Study Course in Memory and Concentration from the 1950’s. It covers most of the basic methods, and you can still find originals online for pretty cheap. It was likely one of the drivers of re-popularizing memory techniques in America in the last century.
Since the techniques are all broadly similar, most of the basic books (and there are many of them) are roughly the same in discussing mechanics, so most of it comes down to practicing to make the system work more quickly for you. Other good places to start include Dominic O’Brien (see above) or The Memory Book: The Classic Guide to Improving Your Memory at Work, at School, and at Play by Harry Lorayne & Jerry Lucas. Once you’ve got one of these down you can hone and improve your techniques using some of the ideas, tips, and tricks on Josh Cohen’s site and forum Art of Memory.
Josh has a pretty good comprehensive list, including some really great historical stuff which goes beyond the “techniques” material. I’m most of the way through Frances Yates’ book and finding some of the history and philosophy fascinating, but I’m probably a rare exception in this area of academia. I keep a short list of books related to memory on my GoodReads account.