Here’s my take on this.
Changes in behavior are often the first thing people notice. This could be increased secrecy with a phone, sudden changes in their routine without a clear explanation, or becoming emotionally distant. These aren’t definitive proof, of course, as stress or other personal issues can cause similar changes.
When it comes to confirming suspicions, you have a few ways to approach it. Using a monitoring tool like a location finder is one method. The main advantage is that it provides factual data, which can remove the uncertainty from the situation. You get clear information about their whereabouts. The other side of that is that you need to be prepared for what you might find. It’s a very direct way to get answers, for better or for worse.