What you need to know to solve all 243 riddles in Arkham Knight
Recently, in my effort to 100% complete Batman: Arkham Knight, I have been scouring the streets of Gotham for riddles, Riddler trophies, and breakable objects.
This can be an incredibly tedious task, but here are three things that you can do to make all 243 riddles much easier.
Keep an eye out for green
Throughout each island you will see thugs and cars highlighted in green. You need to go to them when you see them and interrogate them. They are Riddler informants and will give you locations on the map where riddles, trophies, breakable objects, and bomb rioters are. Be sure to clear the area around the informant so that you can press Y/triangle to interrogate them. Be warned: if you beat the informant unconscious, they can't give you any information...because they're unconscious.
Image from gaming.stackexchange.com
Above is one informant who actually works for the GCPD. Go up to him and press Y/triangle to get information. Others throughout the city you can find just driving around, or gliding in the sky using your Detective Vision. Once you get intel it will appear in your map and you can set waypoints to specific riddles
Be ready to counter an informant
Seeing as how the informants are so important, you must be ready for when they do not want to give you information. It took me a while to figure this out, but when an informant tells you that they don't want to talk, they will swing at you. When this happens press Y to counter them, and the interrogation will continue.
This way you don't have to waste a perfectly good informant. Again the informants make this whole ordeal much easier, it is honestly easier to find the informants and get the riddles on your map than it is to use a guide.
If it's green, take care of it.
You'll notice that upon receiving intel from informants, breakable objects and bomb rioters will pop up on your map. These aren't the riddles you scan, nor are they trophies, but they are amongst the 243 total riddles. Go to these and take care of your business.
If you have any general questions about the riddles let me know in the comments, I would be happy to try answering them.