When doing a running jump, Lara always runs two steps before taking off. Taking a long run-up does not make her jump any farther. On the contrary, a long run-up can result in Lara accidentally running off the edge or jumping too soon and missing the landing on the other side. So unless Lara is being chased or trying to beat a timed trap, take an extra moment to use this simple trick.
To set up for a running jump, first walk Lara to the spot where you want her to take off, usually the edge of a ledge. Line her up facing the spot where you want her to land. (If necessary, use walk, sidestep, pivot and look to get her into position.) Hop back once (tap Back). Then press and hold Forward and immediately press Jump, and Lara will run two steps and jump on the third, taking off right at the edge and land precisely where you're aiming. Of course, you can also press and hold Action while Lara is in the air to grab at the end of the jump.
Set up standing jumps similarly. If Lara needs to jump and grab a ledge opposite, walk up to the edge before jumping. If she needs to land on a flat spot ahead, gauge the distance (based on the number of blocks you need to cover, as described above) and step back if necessary before jumping. And remember that pressing Action shortens the jump, so don't grab if it's not necessary.