Before I go spotting, I check the arrival boards on Flightradar24 for the airport I will be spotting at.
Another great website I use is https://jettip.net. This subscription-based service will automatically filter through the scheduled aircraft movements for an airport and point out the “special” movements. Here’s an example from KBOS yesterday:
The screenshot above depicts special aircraft movements at KBOS, with the “AvGeek” movements being highlighted. I absolutely love JetTip, and I highly recommend it! It’s $5/month, FYI. Have fun spotting! :)