There are many drills that you can use to develop this part of your game. The trouble that most people have with these shots is that they worry too much about the shot and not the position, or vice versa. Many of the rail drills I have come up with deal with the multi-task process of making the shot and attaining position on the next ball. A good way to progress the drill is to attain position at different locations by experimenting with different speeds of stroke. Many of the drills I have made available here deal with this process, as do the drills set forth by Bob & Eric at the San Francisco Billiard Academy. This drill here is an example of combining the two tasks, while at the same time concentrating on control of your stroke. The balls are shot in a color pattern, as follows:
1 then 9 (Yellow)
2 then 10 (blue)
3 Then 11 (red)
4 then 12 (Purple)
5 then 13 (Orange)
6 Then 14 (Green)
7 then 15 (maroon)
8 ball is last
You must also stay on the side of the side of the table as shown in the diagram.