Use SOS DP when you see these patterns:
"For each subset, aggregate over all its subsets (or supersets)." Direct SOS application.
"Count pairs where one bitmask is a subset of another." Precompute subset sums, then query.
"Find if there exists a subset with property X contained in mask." Store boolean flags, SOS computes OR. The constraint (or values up to ) signals bitmask techniques. If the problem involves subset/superset relationships, think SOS.