Hands are probably going to be the most deforming thing on your mesh so it’s important to have geometry that facilitates deformation there. If you can think about the proper topology that certain joints and bends are going to have then all you really have to think of is modeling the topology that bridges these joints. The wrist finger and palm are expected to bend and deform in generally the same radial way while the palm is kinda just a soft blob that is going to be absorbing the tensions for the thumb’s two axis of radial movement from the wrist. Here’s a gif I made showing how different geometries facilitate certain deformations. The middle one is the one that I use probably the most for knees and elbows.

For fingers I also use a variation of the middle topology to really give the knuckles of the finger that volume feel at the cost of pinching on the other side. But this is safe to do with fingers since if the fingers are clenching that you probably aren’t looking at that side of the fingers anyways. It also really depends on what kind of style that you’re going for and if you are doing subdivision modeling. This puts most of the stretching on the outer knuckle(so if there was a texture there it would appropriately stretch and compress just like in real life) and the pinching happens on the inner knuckle(which is mostly unseen).

This is the same hand topology I used for my Corfagrigus model(four hands!). The fingers were mostly bending inwards so I used the topology of the above gif which put all the major stretching and deformation on the outer knuckle of the joint to maintain a silhouette.

And for Apsis’s monster-claws as well give special attention to the outer deformations with the same facilitating “Y” shaped topology and facilitates with the stretching that would occur if her fists were to be fully clenched. Though it seems the topology is hidden in the “knuckle-spikes” details, the topology is actually there.

Also a peek at the knees which use the middle option of the first gif which contain all the major stretching/compression and deformation to only happen behind the knees.

Here’s a hand I made for a commission I’m working on right now. This is subdivision modeled and is stylized with attention to the silhouette so when it isn’t smoothed it looks a lot more bloated and silly than it actually is but the simplified topology is still there.

The nature of subdivided surfaces allow you to do all sorts of facilitating topology tricks and can handle stretching and pinching much better due to the nature of implicit surfaces. A lot of the time it even works in your favor and appears to simulate actually deforming flesh or clothing.

As an example of this here’s a variation of the middle option with an added loop to collapse into which adds the pinching effect while the triangle-shaped 4-sided polygons on either side of it somewhat “contain” the pinching to only happen there.

Here’s the topology above flattened out so you can see that the two quads on either side of this added loop are encompassing the compression happening at that loop.

And finally here is that hand smoothened.

This is a stylized render so there’s no details on the knuckles but I have enough geometry there to support the deformations that will happen should any of the fingers clench. The palm has an extra loop that wraps around to the top of the hand to support any swivelling that the thumb might do and “contain” any deformations it would do to the rest of the hand. Same goes for the “webbing” between the fingers.

So I guess the main tip is to try and facilitate the anticipated deformations of your joints and to try and “contain” deformation movement as much as possible within your topology so you can work with the changes in volume and shape. Then most of the rest of your geometry is mostly linking the surfaces between these joints. Model it’s movement.