Son was offered at a few schools. In all cases, the communication (email, texts, calls) volume and frequency increased significantly and became more timely. That was a telltale sign. Offers for unofficial and official visits were extended and incentives offered. One school made the offer of setting up a meeting with the Dean for his intended college. Clearly the message is we want you, and they followed through.
The truest tell-tale sign was coaches actually doing what they said they were going to do, and doing in the timeframe they said they would do it in.
Just my experiences and observations. Best of luck!