The height at which darting will take place depends on the terrain, particularly the extent of tree and bush cover. Set the dart gun to the appropriate range. If the helicopter pilot has experience, allow him to guide you and to indicate to you when to get ready, when obstacles are approaching, when the animal is likely to veer off, etc. Select the animal to be darted and, if necessary, separate it from the herd. Be prepared to make split-second decisions regarding firing of the dart.
Misses are costly.
Approach the animal from behind. Dart sites to use are the rump, the upper hind legs, and either side of the tail. The lumbar muscle mass can also be used, but the target is smaller and the chances of abdominal penetration are increased. Avoid hitting a surface that is not perpendicular to you - the chances of deflection of the dart are reasonably good. Avoid making too many 'aiming' movements with the dart gun - allow the helicopter pilot to bring you to within darting distance above and behind the animal.