seashoreCM: that's a good note about booking 330 days out for key travel dates around the holidays. Airfare sales are very limited around holidays, so if you are planning a trip around the holidays (e.g. July 4, Labor Day, Thanksgiving, etc) and find a good fare well in advance, it's a good idea to snap it up.
cigar95 also makes a good point about "web fares." Make sure you read the fine print. However, over the past two years or so, I've found that most prices quoted on web sites are the same as what a reservation agent will give you. When I was still hesitant about the whole concept or security of e-commerce, I would research fares online and then call the airline directly to book my tickets. 95% of the time, I would get the same price.
My one experience in requesting credit because the fare had dropped, happened on a Delta flight last year that I did book online. When I called an agent for a credit, they gave me a voucher ($100) without a problem. But, just to be safe, make sure you read the fine print for "web fares" or better yet, call the airline if you have any questions about their credit/voucher policy.
And doc hog raises a good point about Southwest. You can't book 330 days in advance on this very popular low fare airline. Southwest doesn't allow ressies more than 5-6 months out. If Southwest generally offers good airfare on your route, you may want to wait until they offer ressies instead of booking on another airline--unless you find a really great deal, of course!
I love hearing all the helpful tips and experiences on these boards! Thanks everyone for sharing.
P.S. cigar95, that's also awesome about your $187 r/t fare from LAX!!! I've seen those fares, but they never work for my travel dates or are sold out when I finalize my plans, since I tend to procrastinate. My upcoming trip in two weeks (hurray!) is at $240.