I'm still a newbie, being that we just began running HRC seasoned tests this spring, but what I liked to do the day before test was to run a few marks at test distances, as well as a couple of blinds. I didn't really do much in the way of training, other than making sure that the whistle sits were quick, and the casts were taken. I also tried to keep it as fun & light duty as possible. I would also try to get in 1 walkup & a diversion.
I like to do some heel/sit drills to get the dog thinking and working with me the day before a test. It does help with going to the line and the walk up. If I do marks I try to set up something that he'll be successful with as a confidence boost. I also try to run a 3 or 4 marks and a blind the morning of the test to take some of the edge off if I can find a place to do it.
I like to run a singles starting with a middle distance flyer, pick it up and then with bird in mouth I throw a short retired bird converiging with the flyer. The short gunner retires when I take the bird. I send after cuing the dog "easy". This works on checking down for a short retired gun in front of a visable flyer station. Then run a long retired bird tight to the back of the flyer station. This works on driving past the flyer after having just checked down for the short bird. All elements that you may see in a test or trial but as singles to help ensure success.