The best strategy to get good seats on LH without paying is to check in before the 23hr check in time. They say that you can check in at T-23, but in practice, check-in opens several hours before that for on-line check-in. When you do that, you can select seats. Due to the policy of charging for seat assignments, the seat map in Y seems to show as wide open right up until check-in opens.
You can also bid on upgrades to premium economy if you want to try that. See the LH forum for information on bidding on upgrades.