You need to get used to zooming in and out of your image and getting around quickly.
Here are some recommendations-
Command + Space bar - This will toggle you from your current tool to the Zoom tool.
Space bar alone will toggle to the Hand tool so you can move around while zoomed in.
Command + minus - Zoom out by steps
Command + zero - Fit image on screen
All these tools can work together to create a selection
*Hold Shift to add to an existing selection and Alt/Option to subtract from one.
Marque tools - Elliptical and Rectangular - Hot Key M
Click and drag to create the selection.
Hold the Space bar to reposition the selection while you are creating it (dont let
go of the mouse)
Lasso tools - Free form, Polygonal and Magnetic - Hot Key L
Free form - draw a selection with your mouse. When you let go it will close the
selection.
Polygonal - Click to start then click at next corner keep clicking. Hit enter to close
or click at the first point again. Click esc if things go bad.
Magnetic - works on areas of high contrast. Click to add your own anchors.
Wand tools - Magic and Quick Selection- Hot Key W
Magic Wand - works with color. Tolerance setting in the preferences controls
how sensitive the tool is. Check Contiguous to limit the scope of the tool.
Quick Selection - size is controlled with brushes pallet. Command + Right
bracket to increase size, Left to decrease. Smaller brushes make a more refined
selection.
Move Tool - Hotkey V - Toggle to it with Command. Hold down Shift to move straight
Your Best Friend -
UNDO - Command + Z (one step)
Command + Z + Alt/Option (multiple steps, up to thirty)
History Pallet - take a snapshot!