If you're going to actually spend time bounty hunting, do get the kill warrant scanner. The additional bounties do add up. And yeah, if a ship looks tough, e.g. Expert in a fighting crate, then you might want to check bounty in your left HUD screen. I typically just waste everything that's Wanted, with a warrant scan before I open up - only rarely are they small rewards.
Also, remember to only attack the ships that appear as Wanted BEFORE you use your KWS on them. Don't attack someone who isn't Wanted in the system you're in, as a general rule, lest you accrue bounties of your own. Unless of course it's Anarchic, but that's not usually where you bounty-hunt anyway.