Every artist has his or her own style, but here are some helpful tips I’ve learned during many years of drawing and art classes:
A can of hair spray can be the solution to smudged drawings. If you spray a light coat of hair spray on your drawing, it will help prevent the graphite from smearing. Don’t forget to spray outside or in a well-ventilated area, and do not overdo your spraying. A light coat is enough. It is not completely smudge proof, but it helps.
To prevent smudging with your hand, place a piece of paper under your hand and move your hand on the scrap piece of paper instead of your drawing. Don’t wipe any eraser shavings off. You can either blow them off or use a clean, dry paintbrush to carefully wipe them away.
Only draw on one side of the paper in sketch books. It may sound like a waste of paper, but it will prevent drawings from smudging each other.
Don’t forget shadows. Shading makes drawings better. If you don’t have drawing pencils with different styles to create shadows, I suggest using a dull pencil (not a mechanical). If I don’t have my drawings pencils around, I start with a mechanical lead pencil then switch to a regular pencil to do shading. It prevents pencil marks. Don’t smudge in the shadows; color them in with the pencil.
If you want to add some color to your drawings, but you are worried about messing up your pencil drawing then photocopy your sketch and use the copy to either practice with or use as the colored drawing. You’ll also be able to keep the original pencil sketch without color this way. Running over your drawing with pen also works if you feel confident to work with ink.