First of all, you need to learn the basics of releasing a straight ball, which goes straight at a 90 degrees angle. You also need to learn about how to hold the ball in a proper manner to avoid making it swing.
You should keep an eye on the target while making up your mind when releasing the bowling ball. It will help you keep the target in sight and will make it easier for you to bowl a strike with a straight ball.
Concentration is the most important aspect when releasing the ball. You need to aim at the second row of the target as it is the most effective area to bowl a strike with a straight ball.
Try to be as flexible and relaxed as possible as this plays a significant role in the smooth release of the ball. Do not try to put stress on any of your shoulders or arm muscles. It is very important to release the ball in a free fall manner which is quite effective when you are performing a straight ball release.
While releasing the ball, you need to make sure that you throw it when your bowling hand comes in front of you. If you release the ball from the side, it will lack power and you will not be able to bowl a strike with a straight ball.
Your chest and arm should also move in a straight 90 degrees angle which will produce the desired results. Make sure that after releasing the ball, you give a complete follow through by keeping your arm fully stretched in front of you.
Always try to maintain your balance, as that helps in throwing the ball in a perfect way and chances are high that you will bowl a strike with a straight ball.