Online check in 24 hours in advance is a great opportunity to get the premium seats. On the A330 routes, row 11 A/B, 11 H/J are some of the best economy seats on the plane (they are in a mini cabin with only three rows and have extra leg/knee room). The problem is that these seats frequently get snatched up shortly after online check in opens up at the 24 hour mark. As an elite member, you are able to get a complimentary, space available upgrade to a premium economy seat which can be done at the gate, but it is sometimes safer to just pay the $35 if there is a specific seat you want. (On the 767's, row 11 is also a good bet, but it doesn't offer as much legroom/knee room as on the A330's)