Lara Croft and the Guardian of Light

Easy.

On the first level, you'll come in a room with 6 gems and a red skull placed on top of some jars.
A message will show about the challenge.

Just jump carefully on the 7 jars to get each gem and the skull without touching the floor and you'll get your 1st game challenge reward and the achievement.

You can do it on any level/challenge (you'll have to complete every challenge in the game for 100% anyway) but it's a really easy one and the first you'll encounter.

Here is the video for the Spider pots on the first level and the path to jump without touching the floor. Credit goes to Achievaholics for making the video. You can retry if you fall off or miss a jump .

Whilst playing the game pressing the back button at any point will bring up your objectives. In order to unlock this achievement you are required to complete one of these objectives so you are more than likely to unlock this achievement through natural progression of the game.

The easiest and first time to get this achievement is during the first level (Temple of Light) once you reach 7 spider pots. A challenge message will pop up telling you to jump on all 7 spider pots without touching the ground. This is very easy to complete just start from the right and jump on all 7 pots in a clockwise rotation.

The achievement will unlock as soon as you jump onto the 7th spider pot.

Here is a quick video guide to demonstrate how easy it is to unlock this achievement.