One way I heard to tell if you’re in a dream: Look at a sign or something with words. Every time you look at it, the words will change.
Also, you could look at a computer. Computers don’t usually work in dreams, so that’s a good sign. If it doesn’t work, either you’re dreaming or you’re running Windows.
Jumping out of a window on the 2nd floor never hurts in my dreams while pinching myself does.. Maybe don’t use this to check if you’re dreaming though.