I am using the following strategy:
Short term strategy (up to 7 days): Quick profit can be made only on popular projects that are supported by press and famous people in the community.
Mid term strategy (from 7 days to 3 months): projects that announce solution for important problems and that have strong team, portfolio, sales, community support.
Long term strategy (3 months to 3 years): projects containing a lot of pieces of success, each project needs individual deep analysis.
We gotta also understand that strong projects can give results on any time period and any other projects might not survive even before first version will be released.