The first thing you need to is take your normal stance and grip position. From that starting point, with your wrists, hinge the club vertically without moving your shoulders or arms, until the head of the club is in line with your hands precisely straight out in front of your body , parallel to the ground. You want the toe of the club to be pointing directly to the sky. If it's not, you are not square and you need a refresher.
To fix the issue with your grip, review the drawings from the book "Five Fundamentals on Grip", and reposition your grip to get more in these positions. If you do not own this book, I would highly recommend getting it or trying to order online.
When your grip resembles Hogan's, you will be able to do the drill and have the club come up with the toe pointed directly at the sky. Once it is in that position, simply use your left shoulder, or right if you are a lefty to coil into your backswing from that position. This should put you in a great position to swing back through the zone with a square clubface. If you use your lower body to correctly initiate the downswing, the end result is a straight shot.
Repeat those steps a few times, or everyday then start back in your normal position. You can hinge the club up as part of your pre-game routine or pre shot routine to see that it is still square, and then back down to initiate your swing. You can also do what the pros do, if their wrists are getting tired or injured, they will use the drill the entire round starting with the club right out in from of their hands. Sounds easy but without a square club head at the starting point, you will be fighting your body to make solid contact. Start off square and use a more natural motion.