Learning how to hold the club correctly is not as easy at it seems. Most golfers use an overlapping grip to hold the club. Your grip depends on the type of club you are using and the lie you have. These are all issues that the golfer has to address.
Grip the club at about a 5 on a scale of 1 to 10 when you pick up your driver and are teeing off. Some golfers think that because they have the biggest club in their bag, they have to grip it hard when they use it. Increasing the tension with a driver will almost certainly cause you to lose distance.
Hold your putter at about a 4 on a scale of 1 to 10 when you are on the green. When you are putting, you are trying to increase your "feel" when the ball strikes the blade of your putter. Gripping it a bit lighter will help you to feel the ball and influence its path and speed on the green.
Take your 7-iron and grip it at a 6 when attempting a long chip shot. You will not be breaking your wrists on a chip. Your hands and left side do all the work. Grip the club a little tighter, and treat the chip like an elongated putt.
Grip your 4-iron even tighter when you are trying to blast the ball out of high grass or thick vegetation. You do not want the club to slip and the club face to lose its correct angle when you are going through a heavy impediment like weeds or fescue. You are not trying to do anything with the ball except get it out of trouble and in a position to hit your next shot cleanly.
Go to the driving range and try varying your grips with your clubs. Your grip will vary from club to club, and it is up to you to determine how tightly you should hold yours.
Tips & Warnings
You should never grip the club so tightly that your fingers start to get discolored. Gripping a club easily will help you to hit your best shot.