Mastering selections is a key skill to becoming a Photoshop CS6 master. Here are a few basic Photoshop keyboard shortcuts to get you started on digital photography projects of all sorts:

Task Shortcut (Windows) Shortcut (Mac)
Draw straight lines. Alt-click with Lasso tool Option-click with Lasso tool
Add to the selection outline. Shift-drag Shift-drag
Deselect from the selection area. Alt-drag Option-drag
Deselect all but the intersected area. Hold down Shift+Alt and drag Hold down Shift+Option and drag
Deselect the entire image. Ctrl+D Command+D
Reselect the last selection. Ctrl+Shift+D Command+Shift+D
Hide extras. Ctrl+H Command+H
Fill the selection with foreground color. Alt+Backspace Option+Delete
Fill the selection with background color. Ctrl+Backspace Command+Delete
Reapply the last filter. Ctrl+F Command+F
Adjust levels. Ctrl+L Command+L
Use Free Transform. Ctrl+T Command+T