Zoom Tool - used to get up close to specific areas in the file. useful to do detailed work. Useful to see details of the document. Crucial when adjusting and manipulating the document to make it appear seamless, etc.

Navigator Tool - useful when working up close. One is able to "stand back" by zooming out with this tool.

Hand Tool - useful to scroll/move around the document when viewing it up close.

Bucket Tool - usually useful when an area is pre-selected to be covered with a specific color.

Show resolution - note the resolution of the image changes when it is saved at different DPI. Try saving at 300 DPI, then at 172 DPI, and then at 72 DPI or less.

Burn and Dodge Tool - used to "fix" certain areas that you want to emphasize or de-emphasize (according to your intent). Also can be used to play down errors or discrepancies in the image.

Adjust Levels - used to adjust the high/low contrast of the image. To access this feature select from the top menu: Image > adjustments > levels

Find Edges - used to define the image in strict lines. To access this feature, select from the top of the menu: Filters> Stylize -> Find Edges.

Posterize - used to reduce the number of colors or values of the image. To use this feature, select from the top menu: Image > Adjustments > Posterize, then select a number between 2 and 256. Experiment to attain the effect you desire.

Filters - There are many filters. Access them by Choosing from the top menu: Filter. Experiment with them and choose the one that fits best for your intents. Remember to always keep an original image and make a copy for manipulation.