Today I'm going to show some simple guidelines you can follow to create a reference base to draw a hand. It will mainly focus on how to place fingers and knuckles along with proportions.
1. Create the Base of the Hand Using Basic Shapes
We are going to use rectangular shapes to create the base of the hand and straight lines to define certain heights and important marker points we will use to define knuckle height. I'll be using the Rectangle Tool (M) set on square, the Line Segment Tool (\) and in the last step I will be using the Pen Tool (P) to draw over the reference. All of them are set on Toggle rather than Stroke.
Start by drawing out a rectangle with the Rectangle Tool (M) at a vertical angle, make it long rather than wide (see screen shot). Once you've completed this, select the Line Segment Tool (\) and draw two lines that cut the rectangle into three equal parts.
Duplicate the rectangle and move it so it is placed beside the original rectangle. The bottom edge of the duplicated rectangle shouldn't align with the original, allow it to be placed slightly lower, but just very slightly. Then proceed in selecting the duplicated rectangle, grab the top anchor point and push the rectangle down (resizing it without controlling the proportions) until the top edge of the duplicated rectangle aligns with the first line within the original rectangle. Repeat that same process, only this time, make sure the triplicate is placed beside the duplicate and that the top edge line aligns with the second line within the original rectangle.
Do this a third time, only this time the quadruple should be placed on the right side of the original rectangle. Before pushing it down and resizing like the others, cut the top part inside the original rectangle in half (see screen shot) and then align the quadruple with this newly determined height.
Using the Line Segment Tool (\), create a straight horizontal line. Now select and tilt it at a slight angle (approx. 10 degrees). Place the previously created rectangles onto this line. The bottom right corner should touch the line we just created. We've determined the first knuckle heights and can move onto creating the second and third sections of the fingers.
This is real easy. Select the original rectangle (that is now the middle finger's reference), duplicate it and then move it and place it on top of the original rectangle. Duplicate three more times and place each duplicate on top of the other rectangles. You can allow some room between the rectangles, this defines the area where the first knuckle row bends. For the palm and back of the hand, we are going to draw out a square with the Rectangle Tool (M) , holding down SHIFT at the same time so it's perfectly proportioned. To know what size to make it, make the bottom line align with the bottom edge of the pinky rectangle and the top of the square align with the top edge of the middle finger. Once that done, grab a corner and tilt it so that the top line of the square aligns with the bottom edge of the finger rectangles.
This step isn't as clear cut, so you have to judge for yourself how to shape it out. But to help, first start off by drawing a straight line with the Line Segment Tool (\) that cuts the square in half. Here is where it is less precise; make the line stick out further than the square's lines. I aim for about a centimeter added to each side. Once you've drawn the line, select the Pen Tool (P) and then start drawing out the shape of the palm/back of the hand. One point at the outer edge of the bottom left corner of the pinky then the next where the center line of the palm was previously created, a third point where the original bottom left corner of the square was, a straight line to the right side and then back up to the center line, closing it off at the bottom right corner of the index finger.
The thumb is missing! So, re-use the original rectangle (for the middle finger) and tilt it slightly to the right so the bottom right corner of the rectangle leans onto the right. Place it onto the right middle corner created earlier for the palm/back of the hand (see screen shot). Duplicate the rectangle and tilt that even further to the right, making sure to have the bottom left corner attach to the top left corner of the first rectangle.
Before we continue, use the Line Segment Tool (\) to cut off a quarter at the top of the thumb's rectangle.
For this step we are going to mark the third section in the fingers, since there are three. Using the Line Segment Tool (\), cut the top rectangles of the fingers in half. Then mark the bottom knuckles with quick small lines at the top of the palm/back of the hand area.
Select the Rectangle Tool (M) in the square shape again and then pull out a rectangle that is as wide as the bottom line of the palm/back of the hand. This will define the wrist, the height is kind of guess work, I make sure it isn't taller than half the size of the palm/back of the hand.
2. Use the Basic Shapes as a Reference to Draw a Hand
There! We just created a very nice hand reference for you to work on top off. Of course hands aren't as square as the reference is, particularly the top of the fingers, the left spot right above the wrist and then finally, the lower knuckle on the thumb. You can use the Ellipse Tool (L) to mark those areas out to help you further in the reference.
Also remember that the reference can't draw the hand for you, some areas will be harder to get instantly even with the reference as base.
Finally, grab the Pen Tool (P), Pencil Tool (N) or Paintbrush Tool (B) and draw the hand! Make sure not to forget small details such as the veins on the back of the hand, or nails and knuckle definition.
You can use the same base for the other side of the hand. Remove the nails and knuckle detailing, keeping only the hand's and finger outlining, mirror it and then add the details necessary to define the palm of the hand. While it's easy to draw out a swirly shape for digits or a quick curved line for where the fingers folder, the ones that really define the palm of the hand is the V shape at the bottom and instead of having the index finger's line overlay on top of the thumb, you cut it short and make the thumb's line overlay on top of the index finger's, even going as far as adding a second line on top to define the fold.
High Five! Now You Know How!
We've created the front and back version of a hand with simple shapes for reference. Now that you have a small trick on how to shape the fingers, placing them in any position should make things easier! Or, you can take the simple front view of the hand and try to shade it as realistically as possible. I suggest this great article with numerous methods on shading realistically.