I know one former very quick marathon runner, sub 2:20 who swore by a 3-4 mile run first thing in the morning 3-4 hrs before a marathon.
I struggle with evening races, been at work all day, normally sat at a desk, and not really 'up' for races.
Weekend races you normally wake up with that on the mind. For a long maybe a mile jog to the start, some light stretching but nothing really.
For a 10 k normally 10 minute light jog, 3 or 4 50-100 yard strides and some stretching.

