A weak grip is a common cause of a slice. The good news is that it is easy to check and correct. Looking down on your grip you should see two knuckles on the left hand and the 'V' shape between the thumb and forefinger on your right hand should point to your right shoulder. If you have a weak grip, you will see fewer than two knuckles on the left hand, while the 'V' on your right hand will aim at your chin.
Desperate to find the fairway, there is a natural tendency to guide the ball towards the goal. A desperate approach prevents your arms rotating correctly through impact. To check if your arms are moving effectively, make a practice swing but stop at impact position. The logo on your glove should point straight at the target. If it's aiming to the right, your arms aren't rotating properly through the ball.
To promote correct rotation, make a few practice swings as through the ball were teed at shin height. This creates a flatter, more rounded swing, and encourages you to turn your arms through the ball.
Lower Body Turn
For an accurate drive your upper and lower body need to work in harmony. In your lower body moves too fast your arms are left trailing and a slice is likely.
To correct this fault, try hitting 10 practice balls with your feet together. This drill slows down the lower body, keeping it synchronised with your upper half. This is essential for consistent, accurate drives.