1). Approach an area tactically without being seen to set up a "hide".
2). High angle shots from up high to down low. Have the shooter compensate the distance for the angle of the shot.
3). Estimate distance to an unknown target.
4). Inventory their "shooters bag" for the appropriate equipment.
Are they set up for long periouds without relief? do they have hydration, food, knee and elbow pads, sunscreen, face paint aside from the obvious stuff.
5). Give them a scenario that is an impossible situation, or is unsafe to make the shot even though they are given the "green light" for the target. See if they try to make the shot ( an ego deflator every time).
6). Make them run, climb, jump and then give them a set time to set up and shoot a target under stress and exertion.
7). Provide their ammo and place a dummy round to see how they react to an inert round. Don't tell them they have a squib though.
8). If the snipers are to work in tandem, have them make simultaneous shots through thick glass and score a hit without deflection. Hopefully they are assigned their own guns so thay can keep their same zero. Have them shoot each others "zero" so they will know how to adjust if one of the guns fails.
9). Observance course where they are radioed the description of the "target". See if they write down the information or try to retain it in their head. Then have role players dressed in similar attire and have the sniper pick out the target.
Law enforcement sniping is a whole nother animal compared to military sniping.
Most importantly, let them have their choice of ammo, and provide them with plenty of the same ammo for practice, practice, practice. It took me a year to convince my SWAT commander that the inexpensive 147 grain ammo I was given to practice with would shoot much differently than the 169 HP's I would be using in a true situation.