Things to practice for Straight Pool
Practice the opening 14.1 break with just one ball
Set the 1 or the 5 in their left or right rack position, but without the rest of the balls.
Shoot to pocket that right ball in the far left corner, or left ball in the right corner, and shape the Cue Ball to the lag zone. When you are consistently getting the OB in or close to the pocket and the CB close to the head rail, try the same hit with a full rack.
Practice the 'tight-rack' safes that are unique to 14.1
1 - From 3 to 12 inches away, shoot the CB directly into each of the middle three back balls. Shoot medium soft with a touch of high to freeze the CB to the contact ball while propelling one or more balls to a rail. Experiment with varying speed and english to see what works for you.
2 - Do the same with the middle two balls of each side of the tight 14-ball rack.
3 - From varying distances and angles, shoot into one of the front balls. Leave the CB in 'the crotch' while propelling one of the back corner balls to a rail.
4 - With ball-in-hand in the kitchen, kick the CB off the foot rail to one of the three middle back balls, trying for the same result you got with #1 above.
Practice 14.1 break shots with the triangle as target
Set the triangle where it goes to rack the balls; it is your target. Using the triangle instead of racking the 14 balls is a time-saver for your break-shot practice.
Position one OB near the triangle and CB in hand so you can pocket the OB and have the CB move the triangle.
A good initial goal is to get the CB to spin the triangle. If the triangle spins, you know the CB hit close to a corner of the triangle of balls. Hitting near the corner has two advantages: a soft to medium speed hit is enough to break three or more balls loose; and the CB is unlikely to cling to the pack.
If your break-shot angle does take the CB to the middle of the triangle, shoot hard enough to slide the triangle four or more inches across the cloth. This means you have enough speed on the CB to really 'crack the rack' and minimize the possibility of the CB clinging to a slightly spread rack, a dreaded 'self-safe'.
Experiment with different OB/CB positions to see what your favorite break-balls are. There are lots of book and internet sources for the repertoire of time-honored standards favored by the experts. Try them all.
Practice end-of-frame patterns
Scatter a few object balls, three to six, with at least one of them a good potential break ball for the next rack. Run the pattern until you have the CB and break ball remaining. Set the triangle-target. Shoot the break ball, either spinning or sliding the triangle.
Thoughtfully repeat this exercise 10,000 times.
Practice breaking and running
Position a break ball and CB and the full 14-ball rack. Break and run thoughtfully as far as you can. If you get to a position where you don't have a reasonable shot, play a good safe. Play another good safe.
Start over with a good break shot.
Thoughtfully repeat this exercise 10,000 times.