100 moves of random turns
The 7×7 is scrambled with random moves, the approach used for every cube from the 5×5 up, including at WCA competitions. With six layers to mix in every direction, the sequence is 100 moves long: outer turns, two-layer turns and three-layer turns on all six faces.
Starting orientation
Like the 5×5, the 7×7 has a fixed centre piece on every face, so the starting orientation is unambiguous: white centre on top, green centre facing you.
Getting 100 moves right
Scrambling a 7×7 by hand takes a few minutes, so accuracy matters more than speed. Break the sequence into groups of five, say each move as you make it, and check the finished cube against the preview before you start the timer.
Practising the 7×7
At WCA competitions the 7×7 is a mean of three. Practise the same way: three timed solves from three scrambles, and look for the stage (centres, edges or the 3×3 finish) where the time goes.