If you want to remove the background, you can use this shortcut by first selecting the object to keep, and then then pressing this shortcut to invert your selection. Sometimes it is easier to select an object that you want to keep instead of everything that you want to get rid of.

⌘/Ctrl + shift + I inverts your selection. This will flip black to white and if your image is colored, it will instantly invert the colors. This is nice when you use a masking or selection tool, but you mistakenly make it backwards.

⌘/Ctrl + alt/option+ C brings up your canvas size, so you can add more to your canvas (or take some away) without having to create a new document and move everything over. ⌘/Ctrl + alt/option+ I brings up the Image Size dialog box, where you can control resolution, image size in pixels, inches, etc. Here is a list of common, practical Photoshop shortcuts for everyday use. Instead of taking 2 hours to work on a batch of files, you could end up finishing in an hour and a half. But, when you have to work on dozens and dozens of images and files, each keystroke can add up to minutes before you know it. If you are working on a single image, then you may not see much improvement. One easy way to save time is to use keyboard shortcuts instead of flipping through dozens of different menus. This makes time efficiency important for all Photoshop users, regardless of profession. Usually, all of these professions are paid an hourly rate, especially if they are freelancers. Web designers use it to mock up their sites before slicing and coding them, photographers and image retouching specialists use it to enhance and improve photos, and graphic designers use it to create work for print and other mediums. Photoshop is the tool of choice for a wide variety of creative professionals.

Shortcut to save as in photoshop