How can I practice drawing the human body?

You can practice drawing of you hand and fingers.

take a mirror and look your face with different expressions.

and try to draw those expessions nose,eye,leep etc.

and you can draw human figure drawing with the help of your family member tell the to stand and give different poses.

Start from studying your own body and see yourself in mirror by know your body you can start understanding more or less every human has similar features but at the same time distinct features . Gradually once you made an habit of that ,shift to great masters like Leonardo , Michelangelo and Indian yogic poses for excercise from there learn how human figures bend and structure is . 

Use an anatomy book to understand what's below the surface but think about each muscle in 3D. Don't draw the muscles as a series of lines. Draw them as sculpted spheres, boxes and cylinders. With that being said, you don't always have to actually draw spheres and boxes on the page.

The human body is a complicated and fascinating thing to sketch and draw. It helps to have a solid understanding of the different parts of the human anatomy, as well as their placement on the body.

In order to learn how to draw anatomy correctly, you should first study from life models or from reference images. Draw from life models if you have the opportunity, as it will give you a sense of realism in your sketches.

Drawing from reference images is an excellent way to practice without having a live model handy.

It’s important that you take time with both techniques so that you can practice your skills and gain a better understanding of how the parts work together.