One point to add here. While dscan isn’t a 100% guarantee of safety (nothing in EVE is), there are still some things that you can watch for depending on what you are doing in dangerous space.
As mentioned watching local is important, as you can see who is coming and going. One really important thing to watch for on dscan is not just ships, but combat probes. If you see those come out, and if they seem to be getting closer to you, somebody is hunting you and it’s time to bail out of what you’re doing and get to safety.
Of course, if you are at a warpable anomaly, like a data site, then the hunter can warp to that cloaked (or be camped there waiting for you) with no probes needed, so looking for probes won’t keep you completely safe either, but these things can help you mitigate that risk.