Julieanne Kost's Blog

PSCS5 – Check the Protect Detail option in the Options bar when using the Sharpen tool to selectively sharpen and enhance small areas in an image with dramatically better results.

Option (Mac) / Alt (Win) -drag with the Smudge too, to smudge with the foreground color (instead of the colors in the image).

There are several tools grouped together in the tool panel that can be temporarily swapped. For example, to temporarily toggle between the Slice and Slice Select tools hold the Command (Mac) / Control (Win) key. Similarly, Option (Mac) / Alt (Win) will toggle between the Sharpen / Blur tools and the Dodge/Burn tools. With the tools that don’t toggle (the Sponge tool for example which is nested with the Dodge/Burn tools), you have several ways to select it – you can manually select it from the Tool panel, or use the Shift + O to cycle through the Dodge/Burn/Sponge. And of couse you can always assign your own shortcut keys via the Keyboard Shortcut Editor (Edit > Keyboard Shortcuts).
Note: a little known advantage to using the Option (Mac) / Alt (Win) to toggle between the Sharpen/Blur and Dodge/Burn is that the brush size stays the same between the tools (although other options are not connected).