Image Size - You already know how to use this feature (access this feature at the top menu: Image > Image Size). The following is a brief explanation that will help you print good images consistently.

A window with options will appear when you choose this feature. The main thing to keep in mind is your DPI and its relation to the overall size of the image. For printed material the recommended file size is around 300 DPI. You can print it at a lower resolution, but it's not advisable to go below 172 DPI. Whatever resolution you choose, this one should be consistent for your image(s), whether its 2 x 3 inches, or 20 x 30 inches. If you don't do this, images when copy pasted from one file to another will appear either too small or too large.

Increase in DPI (dots per inch) provides reliable image detail. The less dots per inch, the less detail the image will have.

Images printed from the web are usually 72 (DPI). if you print this images, you will notice pixelization. If you wanted to print images originally obtained or scanned at 72 DPI avoiding pixelization, then you can change the DPI, while keeping the dimensions of the image the same. This is strongly not recommended.

To change the image dimensions without changing the DPI, enter the desired dimension for the width and the height. If you have the option"constrain proportions" selected at the bottom of this window palette, you will notice that when you change one dimension, the other changes automatically. This will not happen if this option is unchecked. You can also do this with the pixels if you desire. Generally you will look at pixel dimensions for the web, and inches dimensions for print material.

If you want to keep the image size but change its resolution, then write down the dimensions (make sure to choose inches depending on your project), then change the resolution to your desired number. If your width and height changes, then reenter them.

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Adjusting color using Channels - Open your image, then select your channels palette menu. if it is not already showing, then select it from the top menu bar: Window > Channels. Your channels will appear in CMYK or RGB, depending on the mode you've chosen to work in. To balance colors, check the quality of each channel by deselecting all of them, except the channel you want to examine. An image with bad color usually has one or more channels either washed out or over saturated. You can choose to adjust the channel to make it balanced. As a guideline the channels should not have washed out areas in dark regions, or washed out areas in already lighter regions.

You will certainly know a damaged channel when you see one, it will look dirty or washed out. To adjust the colors using channels, make a copy of your image at the top menu select: Image > Duplicate. A copy of your image will appear. Keep this one on the side as a reference. Then select the channel you want to work on, by making all other invisible. Then adjust your colors as follows: Select Image > Levels, in the color option bar will read by default "RGB". Choose the color you desire (red, green, blue). When you have a well balanced channel, meaning your darks are darks and your lights are light with a decent definition across, recheck the other channels and compare to your image copy. Repeat this process until you are satisfied with the color. Then print to make sure you have the desired print. Repeat until satisfied.

If you find that you want certain colors played down while keeping others intact then use channels as described above, then choose Color Balance and/or color saturation. Repeat until you have achieved your desired results. Always keep a copy of your original, and make sure to go back in your history if you find that you've damaged your image when experimenting.

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Mask Layers - are useful to create images with intricate shapes based on parts of other layers without cutting and pasting the shapes. You can think of the shape as a "whole" in the same way that empty areas function in a face mask. According to where you move the mask, you will get a visible area of the underlying layer.

To create a Mask Layer, make a selection on your desired layer, then in the layer menu at the bottom select the small square with a circle inside (Add Layer Mask) A mask will appear according to the shape you created. To move the mask select the mask on the right of your mask layer, to move the image that is masked, select the image on the left.