Book collecting can be a disease, as anyone who loves to read will tell you. Every time you look at your shelves more books have appeared. Perhaps they crawl in during the night; you would swear you didn't buy that many. And when you move, it is depressing to see how many boxes the books take.
However, this is not to help you wonder how "How to Dig Clams and Recipes for Cooking" got on your shelf when you live in Indiana. This is serious.
You have decided it is time to invest in books. Perhaps you've read that the first edition of Harper Lee's To Kill a Mockingbird was recently valued at $27,000. And, of course, you know some of the ancient, say 16th Century, books go for thousands of dollars as well. Excellent idea, but to insure your happiness, not to mention stopping the bewilderment of your heirs, you need information.
No. 1 - Most important rule. Collect what you love. This can be a beloved author, a favorite subject such as local history, or science-fiction; anything of lasting interest to you. If it doesn't continue to thrill you, drop it. If it does, you can have the deep satisfaction of owning the books, biographies, and perhaps, if a living author, even personal correspondence with the writer. Or becoming the acknowledged expert on local history and the respected authority on science-fiction or whatever you have chosen.
No. 2 - As with any other field, become as knowledgeable as possible about terms used in The Trade. The old standby is John Carter's ABC for Book Collectors, first published in 1952 with the latest copyright of 2008. Standard terms enable you to know if the dealer offering a book is a professional or amateur. (Tip - "good condition for its age" does not cut it.) It will also mark you as not entirely an amateur when you begin.
No. 3 - If you invest in the stock market, of course you do research. Books are no different. This was formerly much easier, as most book dealers sent lists or even lovely catalogues. The internet has changed this. While some sellers still do lists and catalogues, the majority now list their acquisitions on various internet sites that specialize in books. But a word of caution there; there is often an enormous range of prices, along with poor descriptions, making it very difficult to tell a fair price. But again, time will help you decide on the the good sellers who list there. It is also tricky to deal only with internet auction sales; they are said to be rife with misrepresentation and even downright fraud.
Standard auctions can be very good; start with the well-known international ones, such as Swann, Christie's, Bonham's, and Sotheby's. Most cities have branches of these big ones, although you can find excellent local ones; PBA in San Francisco comes to mind. Attend the ones you can, or ask to receive their catalogs.
The best choice is to form a personal relationship with a few dealers you trust. There are also book fairs in different cities around the country, and if you live in the area, do go if for nothing more than enjoying the variety of offerings and getting a feel for the prices. You are also likely to meet some dealers in the specialty you have chosen, a potentially good source for you. If the bookseller is also local or nearby, best yet.
Another fine area of research is your local library. If you hear or read of a book possibly of interest, get it from the library. If it isn't what you want, no harm done and you haven't bought the book. Interlibrary loan is terrific for this.
These rules will get you started; the longer you collect, the better you can judge. And, judging from my own experience, there is nothing more joyful than welcoming a new baby or a book you have been seeking for months or even years. The world suddenly becomes a truly wonderful place.
One last comment from my own experience. I cannot stay out of bookstores when I travel, even if I'm not searching for anything. So many times I have had a lovely time just looking at books and then I look at my watch. I cannot have been here two hours! Surely only twenty minutes. Nope; two hours it is. So I have decided browsing is a mild form of self-hypnosis. It has taken me out of all my cares and into a wonderful grotto of authors and illustrations and past and present centuries. I feel relaxed and dreamy and happy with the world. And doing a bit of heavy breathing; ah, the smell of old books. The feel of a solid book nestling into my hand. Magic.