Let no one think that being a wingman is supposed to be fun without responsibilities. This is HARD WORK if done well, and the feeling of reward is directly proportional to the amount of effort expended in doing it right. Take a moment before the flight to stand by lead's airplane and visualize what the picture will be in the air. Look for prominent parts, panels, paint lines and control hinge-lines or positions for use in positioning. Any idea is better than none, here.
Dissimilar aircraft make it hard to visualize airborne, so get the idea on the ground, first.
Be especially cognizant of where the big, hard, sharp, spinning object on the crankshaft will be relative to the other parts of the formation. Route is roughly two wing-spans further out than close formation position, and along the same angle line. Even further out is fine if you don't want to work too hard at staying there. This position demands attention also, but things like radio changes and map folding, fuel checks, etc., can be done without fear of impact during short attention diversions inside the cockpit. If you think instrument cross-checks are demanding, try formation with a damaged aircraft or engine.