well here is a tip. in the beginning follow the the shuttle. shoot the Ties out of the sky first. than go after the unprotected buildings so when the shuttle lands Stormies will not come out. than you have to destroy the shield... then go and destroy every thiong you encounter. at least that is what i do. destroy the turbolasers and rocket emplacements. and try to shoot down the ties. there are even some probe droids in the outer canyons and 2 At-St's.
hope that helps.
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