You must personally eliminate six aliens before 6:30:06 (that’s when the bombers launch).

Always listen for Crabs firing near you.  They sneak up on you and then you die.

Watch your back.

Hit the enemies in this order: Shards, Webs, then Crabs.

Kill the recon shard before he reaches the bridge or your job is a whole lot tougher.

Ignore the initial skirmish below you... as hard as that may be for your heroic side.

Your starting speed is a fairly good speed for the scenario.