The key to successful book collecting is to focus on your interests in a particular genre in conjunction with a selected time period. Narrowing down the focus makes the job more enjoyable and less of a tedious task. For instance, rather than collecting books about Sports Events, consider collecting books about Sports Events during the World War II period. Instead of collecting cookbooks, consider collecting speciality cookbooks from a certain time period, such as 1920-1930. You may also want to collect cookbooks focusing on just vegetarian dishes or desserts.
Dust jackets increase a book's value tremendously.
Dust jackets became popular in the 1920's with the purpose of dressing up a book and increasing the book's worth. Finding an older book with a relatively new dust cover still intact will certainly prove to be more rewarding than the same book without the dust cover. Check the spine's condition as well. A firm spine and pages intact are what a collector seeks. Cookbooks are highly desirable to collectors.