1) Ensure that any soil that will be used matches what is on the field in question. Filling with sand or soils that are not similar will cause long-term problems.
2) Determine if seed or sod will be used, because this will have an impact on the amount of soil required to obtain a level grade. For sod, when step six is completed, it will be ¾” below grade (assuming you are using new sod). For seed it should be at grade.
3) When making a repair remove any vegetation that encroaches the area of repair – if sod can be salvaged protect it by setting it on wet burlap. Also set it in the order that it came out, sort of like a puzzle with the pieces numbered. This will aid in keeping the soil/root zone moist and will aid in setting it back in place.
4) Locate a matching or similar type soil –that is debris free and not to moist to work with.
5) Scarify with a heavy rake or lightly till existing soil but no more than an inch.
6) Add new soil (if depression requires less than six inches of soil add new soil all at one time – if more than six inches add in four inch intervals but blend each level) to a level approximately 20% above desired finished grade. Lightly blend imported soil with existing soil ensuring a bond of the two. Tamp or roll soil, then grade to desired level – use of straight edge is very helpful to ensure accurate grade with surrounding edges. If area is large than eight to ten feet accuracy will be difficult to obtain and total grading of the field might be a future consideration.
7) When grade is attained lightly scarify soil and prepare as a seed or sod bed. Install the seed / sod and keep moist.

I think your grounds crew will find these steps to be highly effective in resolving the problem.

George Bernardon, Certified Sports Field Manager, GCA Management Services Group (GBernardon@gcaservices.com)