It's hard to know if you have gotten the best airfare, and it's not worth fretting about, just give it your best shot.

You probably have your favorite travel site or two. I tend to look at ITA Travel Software for an overview, but don't rely entirely on it because not all airlines are represented.

From what I've seen, the best days to book are Tuesday, Wednesday and Thursdays because that's when airlines more often offer sales.

We all know it's better to buy in advance, but don't get excited and book your seats too far ahead. Four to six weeks before traveling is best. Prices are higher 8 to 10 weeks and 2 to 3 weeks in advance.

If you are a Twitter or Facebook person, you can follow your favorite airlines and get notice of exclusive sales, some of the special fares posted there expire within a few hours.

For a few years I think we could go Travelocity and see all the possibilities in one place, but now we need to check each carrier's booking site to get the true picture. The so-called lower fare airlines like Southwest, AirTran, JetBlue, and Frontier don't adjust their fares as frequently, but you still need to check the other carriers because the fares still might not be the lowest.

You can also look at SeatGuru.com to learn more about the particular airplane you could be flying on. Sometimes comfort is worth a couple of extra dollars.

Oh, and while you're looking at fares, be sure to read the fine print to figure out the extra fees and charges that are going to be added on.