Rare Books 101
Collect books in a subject or of an author of genuine interest that is meaningful to you. Do not follow fashion. Do not collect rare books strictly as an investment but at the same time do not ignore opportunities to see your books appreciate in value.
Once you have decided on an area of interest, acquire the relevant bibliographies and reference books to that field. It is very important to learn the various points that identify first editions, first printings, first issues, first issue dust jackets, etc. Thus armed, you will avoid costly mistakes.
Acquire a copy of John Carter's ABC for Book Collectors. Still in print since it's original publication, it remains the standard reference to deciphering the jargon of collecting rare books and the rare book trade, the language of bibliography (book science), and book nomenclature. Mr. Carter, one of the giants of the rare book world during the 20th century, writes clearly, often with dry humor, on occasion with delightfully 'incorrigible prejudice.'
Save for and buy the best possible copy of a desired book you can. Condition is everything when appraising a book's market value. It is always better to own five titles by a particular author in fine condition than fifteen titles by the same author in good or very good condition.
It is absolutely essential to develop a relationship with a knowledgeable and experienced rare book dealer who can provide guidance and whom you can trust. You cannot go blindly into collecting, nor have the blind lead you in your blindness (EBay). Visit rare book shops in your locality and soon: they are slowing dying out. Definitely use the Internet as a tool but do not depend exclusively upon it for information.