Here are a few basic tips and tricks for working in Photoshop. I intend to expand this section with more information when I get time.
Load a selection from a layer
Ctrl-Click a layer to select its non transparent area
Drag-Duplicate a layer/selection
Hold Alt and start dragging. If you drag a selection it will be duplicated within the layout, if not it will duplicate the whole layer.
Holding Shift in addition will make it drag strictly horizontally/vertically.
Cut off empty areas. Beware! Doing this can lose you a lot of image information. Further modifications may result in ugly colour/brightness steps. That’s why it should be done right at the end.
It is better to use curves where possible.
Drawing vector paths
Essential keyboard shortcuts for artists:
Space – pan work area
B – Brush
E – Erase
R – Blur/Smudge/Sharpen tool (can be handy)
F – toggle fullscreen, hit multiple times for different modes
Tab – hide menus
Ctrl and +/- – Zoom
 – Change brush size
0 through 9 – set brush opacity or any other selected value
up/down/left/right – move 1px
Shift + up/down/left/right – move 10px
Ctrl and G – Group layers
More to come:
> make use of patterns
> Create a dotted line
with a brush (trace a line)
with shapes (repeat transform command)
> Photoshop actions
run a script