I have a couple of rules of thumb on this, as someone who typically travels by air only once a year or so and pays his own way without benefit of "miles" or exepense accounts or - for that matter - a lot of cash.
1) When you see a fare that looks good, take it. Right then. Because if you come back in an hour or a day or a week or a month, it won't be there. Plan everything else - lodging, ground transport, etc., - around that after you get the reservation. (My deliberative personality and I broke this rule AGAIN this summer when I had my finger on the "buy" button for SLC and let it pass, like an idiot. Now it's like $500 instead of $300 and I'm on to another round of the wait-and-hope game.)
2) Look at the big picture when you're looking at air ticket prices. If you think about how much the total trip is going to cost you, after lift passes, food, bed, etc., you will see that getting all wound up about $50 plus or minus on the airfare is probably myopic. Therefore, spend the extra $50 if it means a better connection or a better fit with your schedule. (Unfortunately, if you don't pay attention to rule #1, then you can end up looking at a $500 difference instead of a $50 difference, and that really can be a showstopper.)