There are a lot of really cool things you can do in Photoshop. Just because you can, though, doesn't mean you should. This video demonstrates 10 techniques that are common, but probably shouldn't be.
This video, from tutorial channel tutvid, shows several techniques like using too much bevel and emboss on text, or using a selective colour technique to highlight a single colour in a black and white image. While these techniques are common (and relatively easy), they often draw attention to themselves, rather than enhancing the image itself.
In most cases, the video gives an alternative for most of these techniques. For example, say you want to use the healing brush tool to fix a blemish of some kind. The tutorial advises against "destructive healing" where you destroy the original image. Instead, there's a setting on the healing brush to sample the "Current and below" layers. This lets you put the fix on its own layer without damaging the original. Then, if you need to go back and undo the change later, you can simply hide that one layer.
Some of the advice in this video boils down to preferences. You might think a picture that's entirely black and white except for the colour red is the most artistic thing in the world, but it may not be perceived that way. The tutorial compares this to the cliché shot of a person walking down railroad tracks with a guitar on their back. It may not be wrong, but it's worth knowing the context that your image will be seen in. If you're making stuff for you, then do what you like. If you do Photoshop work professionally for clients, it's good to know what kinds of things to avoid.