Let's start with choosing a desired pose for the subject. In this case, we have a flying/floating pose as Magneto is well protrayed in this manner. After picking out the right position, you may now start with the basic step --- the stick drawing. Always begin with the head down to the feet. In this stage, do a rough sketch. Start by drawing a balloon shape for the head, then proceed with the other parts. Hands and feet are easily followed when they are drawn in elongated pea shapes.
Once you're satisfied with the pose, apply clear guides on the stick drawing.
Now, you can start working on the basic shapes of the subject's body. Since we are dealing with a male character, not to mention, a comic character, try to make the body bulky and heavy looking. Again, start drawing the head first. Make it extra big since we are also considering the size of the helmet which Magneto is always wearing. Then, draw 2 lines crossing each other as guides for applying the details on the face later.
Then proceed with the upper torso. Start with parts that are cylindrical in shape: neck, stomach/abs, and arms.
After that, draw the chest and shoulders by simply creating guides joining the cylindrical shapes. In this stage also, start doing the basic guides for the hands using the stick-drawing technique.
Focusing on the hands, begin applying shapes in cylindrical manner.
Proceed with the lower torso. Same procedure. Start with parts that are appropriate for the cylinder shapes, and end with creating the lines joining these shapes.
Now, we are ready to apply more realistic shapes on the subject's body. Using the guides, you can easily draw details and muscle tones on the character. However, this particular step only deals with the basic but distinct anatomy of a male body. Note that we are still in rough pencilling stage. Here's a link showing how a body of a male is done: http://www.dragoart.com/tuts/1478/1/1/how-to-draw-anime-body-poses.htm. Again, always start with the head. This time, you are now adding the eyes, eyebrows, nose, and mouth.
Next is drawing the torsos. This step involves muscle anatomy especially on the chest, arms, and stomach/abs, and legs. Here's a link to show you the basic muscle anatomy of both upper and lower torsos of men: http://animalodyssey.deviantart.com/art/Anatomy-Piece-167135433?q=boost:popular+male+muscle+anatomy+front&qo=35
After applying the basic muscle tones, you can now proceed to the next stage wherein you do some detailing and contouring of the muscles. Again, with the link provided, follow the guides while you do the referencing. Note that in order to save time, you can dress up the subject already. Meaning, the costume is now made visible. For our subject, here's a reference link of Magneto's classic costume: http://www.eatsleepgeek.com/wp-content/uploads/2009/05/magneto.gif. Let's start with the head. Since we are drawing Magneto, let's put on the headpiece right away. Magneto's helmet covers his entire head and face except the eyes, nose, and mouth. Begin drawing a guide showing two circles on the area of the eyes and a vertical opening from the nose down to the chin.
The succeeding guides cover the rest of the basic costume elements. First, the pairs of gloves and boots both have and stripe-like designs consisting of 3 straps. For the chest gear that holds the cape, it has a u-shape that covers most part of the chest area. Additional accents are bolts lining up the area of the gear. Lastly, the cape. Magneto's cape is usually depicted flowing outward like there's always an air or wind coming from the back of Magneto. You can experiment with the direction.
After you have done all these, proceed now with final detailing of muscles, facial expression, costume designs, accents, and the flow and drapery of the cape.
Next and last step is cleaning up the pencils. After removing the guides, you may now apply the inks on the piece. You have now reached the final stage of drawing magneto the rhardozed way.