Have the broken or damaged item accessible (not buried under other equipment, not blocked by parked vehicles), have a general idea of what you want fixed and any specific concerns, and have someone on-site who can answer questions and approve scope changes if needed.
If the work is on equipment that’s been running, let it cool. If you’ve already tried to fix it and the patch is still in place, leave it for us to inspect, we’d rather see what’s been done before deciding the next step.