Basic Kettlebell Grip Overview
When it comes to kettlebell grip, there are two main styles. Hardstyle (Pavel Tsatsouline popularized this one and most people start with it) and Sport Style (also called Girevoy Sport or GS for short). Both reach for maximum efficiency, but the key in determining what works best for you lies in determining what you want to be able to do.
With Hardstyle (this is true across the whole style, not just the grip, though we're only talking about grip here), the aim is to get the most from your body on every single movement. Let's say, for instance, that you only have time to do 10 total reps in your workout. In that case, you want each rep to be as hard as possible so that you gain maximum benefit. In comes Hardstyle to deliver just that: maximum tension and stress on the muscles, heart, and lungs.
On the other hand, let's say you have time for a longer workout and you want to improve something specific (build a stronger press, for example). In that case, you want to maximize the efficiency of all of your movements so that you can work your selected muscle or muscle group as hard as you want for as long as possible. By increasing your physical efficiency in the movement, you keep the less important areas in your workout from interfering with the real meat of your training session. It's fine for the grip to wear out, but if it wears out before you get to smash your pressing muscles like you wanted, then you've missed a step in how you're approaching your workout.
In my opinion, both varieties have strong merits in their favor and it's just up to each person to choose the approach that best suits their goals.
In the Hardstyle grip, which is what most people learn first, you grab the handle somewhere in the middle of the handle and squeeze. From there you swing, clean, snatch, etc. The aim is to develop as much tension in the body at the key moments to deliver maximum gain from minimum reps. In the case of grip on the press, for example, you would squeeze the bell as hard as you can as you press the bell upwards. Doing this, you'll get a great benefit press-for-press, but you'll often find that smaller muscles (like grip) will wear out before you've hit the volume you want.
In the Sport Style grip, you are aiming to use almost no grip at all. You really want to approach your hand as a connection point rather than part of the active work.
The end goal for the grip style is to have one corner of the bell's handle rests in the nook between your thumb and index finger (the thumb web) and the handle crosses the palm as if you are cutting off the part of the palm that holds the thumb. The other end of the bar's handle should rest down against the wrist, rather than on the palm at all. The effect is one of leverage: you essentially just rest the bell in that notch on your hand (in the way that provides the most structural support for the weight given the activities) and then drive up from the body with all your movements. The grip gets minimal work on each rep so you can go for more reps, more circuits, or more exercises per circuit.
In terms of getting there, the setup is fairly simple. You stand in your swing position with the bell on the ground a little in front of you, as you would before a set of swings, for example. However, instead of having the handlebar of the kettlebell vertical or horizontal, you want it angled about 45 degrees. If you were using double kettlbells, it means that looking down on them, the handles would form a wide V shape.
From here, you reach down and put your fingers around the handle and slide your hand along the handle toward your body until your index finger touches the upward bar of the handle. This is easiest on a competition style bell since those handles come up vertically from the bell. Whichever type of bell you are using, at this point, take your thumb and put it over the top of the bell and use it to hold down your index finger down. It looks kind of like the "okay" hand symbol except for the thumb overlapping the index finger.This is called the finger lock. The remainder of your fingers can stay loosely under the handle to provide support when needed on the swinging motion or otherwise. Here is a video that demonstrates the bell position, hand position and finger lock pretty well: Kettlebell Quick Tip # 4 Fingerlock
If you have issues with callous tearing or pain, you will find the middle minute or two of the video to be particularly helpful. The whole video is only about 3.5 minutes so it doesn't take much time to view.
The key when swinging upward in a snatch or clean is that instead of "punching through" the bell with your fist closed around the handle, you are simply sliding your hand as far through the handle as it will go with the bell staying in the thumb webbing.
The ultimate effect will be so that one corner of the bell's handle rests in the thumbweb and the other upward arm of the bell is along your wrist, as described above. Attached are some pictures that show the hand position in the rack and overhead. You can see how the hand goes as far through the handle as you can go while keeping the bell in the thumbwebbing. This will minimize grip fatigue so you can go about the real work of your training session. Of particular note are the positions of the handle in relation to the wrist and hand.
If you're not sure which type of grip you use, you can either observe the bell position in the rack to see how everything is laying or you can look at the callouses on your hands. If the biggest callouses are on the palm at the base of the ring and pinkie finger, then you are probably using some version of the Hardstyle Grip. Sport Style grip tends to form more even callouses across the base of each finger.
As with pretty much all exercise form, it's less complicated than it sounds. Play around with this grip style some and see if it suits you better than what you've been doing.
I should also note that this is a grip overview rather than an in-depth study which look at all the various subtle differences between GS practitioners, but this is the method I use and it's based on the Fedorenko Method. I suspect that many people will find this grip style to be as transformative for their kettlebell experience as I have.