How do you know if someone is working on you? (good or bad) I'm sure everyone is different but I was just wondering.

if you have suspicions a lot of people will do some form of divination to find out if they are being worked on. (Tarot cards, scrying, reading tea leaves, etc.)

but I strongly advise to consider anything mundane that might be happening to you, such as a regular string of good or bad luck.

What KaliMon said and for me. may sound odd but if you did a cleansing and centering and etc...but yet you feel like some small string or something is still there...its an odd feel... you may want to look into cord cutting