There's some luck involved in fantasy football. It's primarily skill, which is why some of the same people are perennially near the top of the standings. But the goal when creating leagues is to eliminate as much luck as possible.
One way to do that is the setup for acquiring free agents. First, there's the rolling waiver wire. In this system, the strategy depends on players deciding when to use the waiver wire priority, often waiting for that big free agent if they get to No. 1 in the waiver order because making a claim sends them back to the bottom.