Start by sketching the basic shape of the jeans. Pay attention to the folds and creases for a realistic look.
First, get the overall silhouette right. Then, add details like the stitching and pockets. Use shading to give depth. It takes practice to master it!
Well, you need to understand the fabric texture of jeans. Focus on capturing the way they drape and bunch up. Also, look at reference images to get the proportions right. Keep trying and you'll improve.