The Amazing Spider-Man

There are 10 Xtreme Video Challenges in total.

After a few chapters, you will see the first Xtreme Video Challenge indicated on your maps as a blimp. After you complete the Xtreme Video Challenge, another blimp icon will pop-up this time being the Xtreme Race Challenge.
They both are indicated by a blimp icon, however the challenges alternate.
(In other words: after 1st Xtreme Video Challenge is the 1st Xtreme Race Challenge. Then after the 2nd Xtreme Video Challenge, the 2nd Xtreme Race Challenge, etc.)

As stated by Dom2096, The XTreme Video challenges are easy, just keep Spider-man centered. Almost impossible to fail.

Every few chapters, the next sets of Xtreme Challenges will show up. (along with the earlier sets if not previously completed)

Also, being that you can only access a Xtreme Race Challenge after completing that same level Xtreme Video Challenge, it is basically impossible for anyone to get the "A Dash of Spider" achievement before the "Camera Loves You" achievement. So yeah. FYI.

The XTreme Video challenges become available early in the game, and additional challenges unlock as you work your way through the story. You can start XTreme events by finding the "Blimp" icon on your map. After you complete one Video challenge, you'll then be tasked with completing an XTreme Race challenge next. I waited until I cleared the story and then did these, so don't feel pressured to take them on while you're doing your story run.

The XTreme Video challenges are very easy. You simply need to keep a (large) circular reticule over Spider-Man while he performs a series of zip line swings. These will last for 20 seconds to a minute max. Just keep the reticule over Spidey, and you'll get these in no time.