Do you have to "join" star alliance or does it just happen?
Once I hit Silver with US air does that also make me get "preferred" status with the others?

So how do you experts do this....I am currently flying from PHL to BOS so I don't get many miles and just count on the segments to get me up to the preferred status. I currently have 20 segments so 10 more to get silver but with the current US promotion I should hit Gold by the end of the year.
Once I hit status on US air should I start using my CO FF and then work to get status with them?