Experience in Batman: Arkham Origins is used to unlock upgrades for the Dark Knight. As most of you are aware by now, there are quite a bit of unlocks to work towards. Earning XP in the game is fairly easy, but it can still take a while to earn enough to unlock all of the abilities you'd like. Thankfully, Deathmule has put together a quick little guide that shows you how you can earn a good chunk of experience in very little time.
Directions: Before heading towards Jezebel Plaza to locate the Penguin in time for the arms deal, first travel to the Burnley part of the map and head towards the indicated location in the video. Head to the rooftop where you'll find a guard. Let him kill you so you will be saved at this location.
Once you respawn, use the grappling hook and return to the rooftop. Silent takedown the first three enemies, then use a Knockout Smash to silent takedown the fourth enemy. You will receive a total of 8,000 XP. Wait for the save icon to disappear, then pause and select "restart" to respawn from the last checkpoint. Repeat this process as many times as you'd like until you are satisfied with all of the upgrades. It's said that this strategy can get you 120,000 XP in just 15 minutes.
While you're at it, we've also got a complete guide to all of the Anarky Tag locations scattered around Gotham.