Sometimes when creating/editing graphics, it's a one-time job. Other times, you may want to come back and make changes. Here are a few ways to help keep your image easy to modify:

Adjustment Layers

Use adjustment layers rather than changing the image permanently. An example of this is changing the hue/saturation

The destructive way:
Go to 'Image>Adjustments>Hue/Saturation'

The non-destructive way:
Go to 'Layer>New Adjustment Layer>Hue/Saturation'

This way you can modify or remove the hue/saturation adjustment at any time by double clicking it in the Layers window.

Shape Layers

There are advantage to using shape layers over normal filled shapes. Before drawing a shape (ellipse, rectangle, etc), click the 'Shape layer' icon as shown:

This will give you a vector shape, which can be resized without affecting it's quality. The problem with normal filled shapes (the 3rd option shown above) is that once created, they can not be made any larger without becoming distorted.

Another benefit of shape layers is their reusability. When you have created a shape you want to save in Photoshop for later use, go to 'Edit>Define custom shape'.

From now on, the shape will appear in your custom shapes:

Layer Masks

The are many techniques for masking. A mask is basically a layer that will show or hide parts of the layer below it. If you have a photograph and would only like to display a circular selection of the photo, you could just delete the area around the circle.

A better way is to click the button shown to add a layer mask:

Now all you have to do is color in black over all of the areas you want to hide. Color with white to show areas that have been hidden. Now your original photo is still intact, and your layer mask is easily adjustable by double clicking it in the Layers window.

Stay tuned for part 2