Adjusting the exposure and using the Adobe Camera Raw filter
Removing something from an image
Move or copy objects in a photo
How to put a person from one photo onto a new background (or putting two photos together)
How to add text
Saving photos and saving formats that are shareable
It’s a bit of a long one but some really good tips in here that I’m sure you’ll find helpful if you’re new to Photoshop.
He also mentioned grabbing a Wacom tablet to use for your editing instead of a mouse. I use one in Lightroom as well and it is much better and more precise and doesn’t leave you with a cramped hand after working on images for hours.