I would like a pic of the big bug sensors. I've hit a few near his eyes (on/near the moving head).
As for me, here are my tips:
Aim for the first alien that pops up on the left side. Proceed then to any alien above and keep shooting, even if you have to raise your gun vertical.
Shoot a swinging guy. Shoot the guy that pops out of a mid-level window (easier on inside track).
Shoot the crash site aliens.
Shoot the fire hydrant alien.
Shoot above the fire hydrant alien for some window aliens (one with big eyes, one with green eyes)
Shoot the windows near the first spin, and then turn around and shoot the sensors again.
Shoot the big eye-tentacle guy's gun.
Shoot the big-eyed guy. If on outside track, shoot at the alien that hides in the curtains.
Shoot begging alien & its cohorts, and try for the above alien.
Shoot the green eyes in the bushes (easier on outside track)
Bio-scan.
Shoot the dropdowns (gun aliens in the squares). Designate someone to shoot the opposing exhaust port. If theirs doesn't work, pray that they dont shoot you and yours is affected.
Shoot the opposing exhaust after the cars turn slightly. Shoot any green eyes if the opposing car spins (it rarely does)
Shoot the armored alien
Shoot Will Smith
Shoot the big alien and get bonus (if necessary)
That's what I do. Sometimes I max out at/before the armored alien, sometimes I need the bonus, sometimes I do just poorly and get less than 800k (which is when I get mad at myself, unless the gun is messed up).