There's a few tools for figuring out radio stuff. The first is super simple, it just scans through the frequencies and tells you which is the strongest. Most devices will put this in their manual but it's nice to not need to have to look it up.

Once you know the frequency one option is to just take a raw sample at ____megahertz and play it back on demand. This doesn't work for some radio signals because they use rolling codes and it's also a bit inefficient (be VERY VERY careful using a Flipper with a car key fob, because they can sometimes go out of sync and you can't open your car afterwards)

The good news is, for many types of radio signals, the flipper can also determine the protocol and what digital data is being sent- so instead of playing back a 2 second sample of me holding down the "power" button on my lamp's remote, it knows it can just broadcast 0x1234 using protocol XYZ.

NFC and RFID devices are basically plug & play, although only a subset are supposed.