It is very common to find tutorials about making page curls. Many of those tutorials are great, but the final effect is very unrealistic, not because of the quality of the tutorial, but due to the 3d nature of the effect.
Creases and folds are more subtle, instead. They can be created only with clever shading and little or no retouching at all. At first glance they may look intimidating, but as soon as you realize how to create basic creases, you will be able to move on to more complex projects.