Draw the hand before you draw the fingers.
Build a hand study around the palm, the direction of the fingers and the spaces between them.
For your deskA hand reference model or your own hand, a sketchbook and a pencil.
Look for the overall movement
Before drawing a contour, follow the direction from the wrist through the palm and towards the fingers. Put down a light line for that movement. Then mark the outer limits of the pose: its highest, lowest, leftmost and rightmost points.
Treat these marks as a rough envelope. Compare its width with its height. This gives you something to check against as the smaller shapes appear, and makes it easier to catch an oversized finger early.
Give the palm a front and a side
Think of the palm as a simple volume with a front, a back and an edge. Use a few broad lines to show which surfaces face you. Place the thumb as a separate form attaching to the side rather than as another finger in the same row.
Find the knuckles as a group. Their positions change with the pose and viewpoint, so observe their rhythm rather than forcing them onto a straight horizontal line. Keep your construction light enough to revise.
Place fingers with direction and overlap
Mark each finger’s direction before adding its thickness. Indicate changes of direction at the joints with simple connected shapes. When a finger points towards you, compare how much of it is actually visible instead of drawing its full remembered length.
Look at the gaps between fingers as shapes of their own. A narrow triangle or an uneven sliver of background can reveal a proportion problem more clearly than the finger outline. Check which forms overlap before committing to darker edges.
Use detail to explain the structure
Add only a few accents once the palm and fingers sit together convincingly. A knuckle edge, a cast shadow or a short crease can describe a turn without outlining every surface.
Finish by comparing the model and drawing from a little farther away. If the pose is hard to read at that distance, return to the big shapes. More detail is unlikely to fix an unclear silhouette or a palm that is too narrow.
Further reading: Proko: How to Draw Hand Bones — Anatomy for Artists