When it comes to Photoshop, the biggest advice is simple: Concentrate on the important things. The tools, the part of the software that matters, don't get caught up in the other functions. That will get you 90% there.
The main rule with photoshop for beginners is focus on the main tools that are used 90% of the time and nothing else. These tools are used over and over which are the bulk being used for everyday real world projects.
The second rule is, learn the main tool shortcuts.
Also, if you don't know already, you need to know the main shortcuts for basic computer operation.
They are:
Control-C Copy
Control-V Paste
Control-W Close file
Control-S Save
Control-Z Undo (multiple times means multiple undo's)
Control Shift Option S - Save as a Web Image
Option Control I - Resize Image Size
Spacebar - to move around the image
M - square marquee
L - Lasso Tool
V Move Tool
P - Pen Tool
B - Brush Tool
[ ] Brackets size the brush tool bigger and smaller - very important for retouchingC is the Crop Tool
Learn these Tools. Learn the Shortcuts to those Tools.
Q is Quick Mask. Learn the Quick Mask Tool at the bottom of the Tools bar.
Force yourself to use the shortcuts when you can. Take the time out to learn how each of these main tools work and use them. Using these Tools and Mastering them will allow you to edit like a pro.