Marquee Tool

Marquee Tool //    M
Hold Shift to create a uniform shape
Hold Alt to create the shape from the cursor origin
Hold Alt to subtract from selection
Hold Shift to add to the selection
Hold the Marquee tool to reveal rectangle, circle and single pixel
Move selection while creating  //    Hold Shift and drag
Move selection  //    With marquee tool, L click inside selection and drag
De-Select  //    Ctrl+D

Lasso Tool

Lassoo Tool  //    L
Hold the icon for: Lasso, Polygonal Lasso, Magnetic Lasso
Backspace will undo previous clicks
Hold shift to create horizontal, vertical and 45 degree selections
You can zoom and pan while creating your selection
Double click or click start point to complete selection
Take care!  //    If you accidentally double click you can ruin your selection! You’ll have to start over..

Magic wand tool

Magic Wand  //    W
Tolerance //    Sets the range threshold, higher number, the greater range of pixels you will select.
Sample all layers  //    consider all layers or just the current layer.
Select inverse //   R Click, Select inverse. Usually I magic wand the area I don’t want, then invert the selection. Note: Ctrl+i will invert the colours of your image, not the selection!

Copy/Paste Selections

Copy selection //    Ctrl+C
Paste selection //    Ctrl+V
Paste selection to another document in the same position  //
Ctrl+Shift+V. Edit, paste special, paste in place.
Copy layer or group to another photoshop document //    Right click the layer in the layer stack over the layer name, duplicate layer, select the document to paste to in the dialogue.
New layer via copy or cut  //    Right click your selection, make sure you are on the correct layer.

Save Selections & Alpha Channels

Make selection from layer  //    Hold Ctrl and click layer thumbnail.
Save a selection  //    Make selection, right click, save selection. Go to channels tab, the selection appears as an alpha channel.
Make selection from a channel  //    Click channels tab (next to layers)
Hold ctrl, click the thumbnail.
You can add to the selection by holding shift and ctrl clicking on more thumbnails.
Deselect by holding alt and ctrl clicking a thumbnail.

Either hold ctrl and L click to select, or select all (ctrl+A) and Copy (Ctrl+C) the channel.

Fill and Gradient

Fill Selection with foreground colour //   Alt + Delete
Fill selection with background colour  //    Ctrl + Delete
Switch foreground/Background colour  //    X
Gradient  //    G

Layer Masks – Non destructive erasing

Make a layer mask  //    Click the layer mask button below the layer stack.
With the layer mask icon selected, select the brush tool.
Painting in black will erase
Painting in white will bring back
Switch between foreground and background X
You can also make a selection with the marquee tool, then press the layer mask button and a mask will be created of your selection. Hold Alt and click layer mask to hide the selected area with a mask.
Invert the layer mask  // Ctrl+i
Move the layer independently of the mask   Click the Link between the layer and the mask.
Disable the layer mask  // Hold Shift and click the layer mask.
Delete the layer mask  // R Click the mask and select delete layer mask.

Layer Masks – Cut out an object

Create a layer mask  //    Click the layer mask button below the layer stack.
With the layer mask icon selected, select the brush tool.
Hold Alt, Drag Left/Right to change brush size
Hols Alt, Drag Up/Down to change the brush softness
Paint a black line around the inside of the object.
When finished, Alt click the layer mask thumbnail to view the mask.
Use magic wand to select the inside, Select/ Modify/ Expand, 2 pixels, Fill Black (Alt + Delete.
CTRL+i to invert the layer mask. Click the layer thumbnail to return to your image.
Clean up the mask using the brush.