Running is a much-overlooked part of batting coaching, especially for newcomers to the game. Net practice doesn't introduce the concepts of backing up, calling and lumbering about with pads on.
If you are the non-striking batsman, walk through the crease as the bowler is delivering the ball. Not too far, since he could run you out by not delivering the ball and breaking your stumps instead but make sure you are on the move. As with fielding, it is easier to start running if you are already in motion. Also, a 20 yard dash is reduced to 18 yards. Two yards can make a big difference.
If the ball is struck behind square (i.e. in a direction behind the striking batsman, be it leg- or off-side) such that you, as non-striker, can better judge the run, then the responsibility of the run is your call.
If you are the striker and the ball has gone in front of the wicket, then the responsibility of the run is your call.
- NO! means you are definitely not running
- YES! means you are definitely running (do not shout go!)
- WAIT! means you are not sure if there is a run on. Once the doubt is removed one way or the other (a misfield, a good stop) state Yes or No as appropriate.
Make sure the call is loud enough to be heard. There are no prizes for not being heard and thereby introducing doubt, nor is anyone going to laugh at you for shouting.
As you pass the other batsman, give an initial indication of how many runs you think are on, e.g. two or three, but always clarify the next run as you are turning. Whoever is viewing the action is in the best position to do this. Your running partner may slip or pass out so be prepared for such eventualities; don't just charge on regardless.
Even though you may have called for a run, be prepared for the other batsman to shout No! in reply. He may have been caught off-balance or on the back foot and adjudged that he cannot make the run so respect that view. Obviously if he's a fat lump hogging the strike and out of puff try to run him out as soon as possible for the sake of the team!
Once you have committed to a run get the head down and sprint. Don't look at the fielder or anything else, just go for the line. Get the bat down and run it in over the line. Many's the batsmen who should have made his ground but had his bat flapping in the air instead.