I like Richard's paint marker tip.
No second guessing and no unnecessary "double handling".
Simple.
My other tip is just to stay cool when the first highway patrolman pulls up beside you at a traffic light.
Your car is
not too loud (is it?), it's
not rocking from side to side with a top fueller idle (is it?) and that personalised number plate that you agonised over for weeks before deciding on that killer combo is not too ahem, suggestive, for the more conservative members of the law enforcement fraternity (is it?)
Just give the nice man a friendly smile (wetting yourself is not a good look, or feel for that matter) and try to move off without stalling or frying the tyres. Somewhere in between is nice. Relax -- all will be well. Because you know, some highway patrol guys appreciate Cobras too!