The strategies really are simple. You focus like this:
1. Projects that rarely have work - have everything you can attached calling for work
2. Projects that go down often - higher priority to grab work while you can
3. Projects that are less popular - many teams focus on their favored sciences rather than these challenge sites
4. Leave projects like WCG and other fan favorites as backup projects and challenge projects. Those will be the hardest to ever get positioning anyways.
The problem with the point system is that you can squat on points year round on projects that don't have fair opportunity to progress.
Edit: 5. The last thing to remember is if a new project is added the second half of the year, everyone will be re-adjusting strategies/hitting it hard/or letting the waters settle before diving in after it. Mostly just the mega milestone chasers. So, those projects tend to have a little easier time to accumulate position as large teams that have a bunch of 1 box donors will slowly educate them and trickle them on board. Most teams have their positions locked in the second half of the year. The 4th quarter is a shorter quarter and tend to be when the WCG challenges take place. Since large teams have already had all year to accumulate vast points in those projects and partake in the challenges, it is unlikely any challenge contribution will help you gain scoring points. Also, by focusing on WCG at the end... that is typically when Formula-BOINC is monitoring a teams output for the coming year. So, WCG is low scoring. If you want to stay in League 2.... WCG CPU/SETI GPU. If you want to bump to League 1, well.. you focus on projects like POGS that score higher as well as Collatz/GPUGrid.