Another thing to bear in mind (that I found out from previous cars), if you are driving quite hard and your brakes have heated up, then you come to a halt at the lights and sit there with your foot on the brake, there is more chance of the brake pad material bonding to the discs and leaving residue behind - people often mistake this for warped discs but in fact it's just uneven disc surface due to the build up of melted on pads.
No idea if the Lexus suffers with this as I've not had mine long, but it's certainly a problem for other cars...
If I come to a complete halt I usually try to knock it into neutral and stick the handbrake on.