Here is a drill I was taught.
Here is a drill that I was taught a long while back and has helped me A LOT. Start off with the 4 balls (you can use any numbered balls I just used 1-4) set up 1 diamond in on the short rail and two diamonds up on the long rail. Shoot each shot - if you miss one of the four you start over until you make all four in a row. After I make it once I make it two more times in a row. If I miss I start over. When you first start shooting them it doesn't matter where the cue ball ends up. Once you complete this drill 3 times in a row then do the same drill but using a stop shot. Complete that drill and then try a litte draw and then a little follow. I don't do this drill as often as I should but I just started using again recently and I have much more confidence in my straight shots. You can also use this drill at different lenghts.
Here is a drill that I was taught a long while back and has helped me A LOT. Start off with the 4 balls (you can use any numbered balls I just used 1-4) set up 1 diamond in on the short rail and two diamonds up on the long rail. Shoot each shot - if you miss one of the four you start over until you make all four in a row. After I make it once I make it two more times in a row. If I miss I start over. When you first start shooting them it doesn't matter where the cue ball ends up. Once you complete this drill 3 times in a row then do the same drill but using a stop shot. Complete that drill and then try a litte draw and then a little follow. I don't do this drill as often as I should but I just started using again recently and I have much more confidence in my straight shots. You can also use this drill at different lenghts.