In fact, according to this (somewhat dated) article in the Atlantic, about 90% of computer users don't know how to use CTRL+F.
So here's a short list of 8 keyboard shortcuts you need to know, if you use computers regularly (a quick note: as a PC user I've given some preference to PC commands in my explanations, but have tried to list each command with PC & Mac controls. I'm sorry in advance if any Mac users get offended or feel slighted...you're people, too).
1. CTRL+F / Command+F: Find
I should probably lead with this one, since it was mentioned in the above statistic.
If you want to find something quickly on any web page, using any major browser, simply press CTRL+F / Command+F and enter your keyword. You can move through the entire web page for all mentions of it.
I use this all the time when searching for keywords in text-heavy documents. You can also use this in Microsoft Word, as well as in PDF documents.
2. CTRL+C / Command+C: Copy
If keyboard shortcuts were all a pack of gorillas, CTRL+C would be their silverback, alpha leader.
This is the go-to shortcut used across almost every word processing application to copy text. Microsoft Word set the standard for a lot of the keyboard shortcuts used by developers in other applications, but CTRL+C has to be the most prevalent (no, I have no statistics to back this up, it's just how I feel).
3. CTRL+V / Command+V: Paste
Of course, if you're going to copy something, you're probably going to want to paste it somewhere else.
The CTRL+C + CTRL+V one-two punch combo is a must-have in your arsenal in keyboard shortcuts. Whether you're copying e-mail addresses, copying text from Excel into Word, or copying objects in programs like Photoshop, this is something most users will use frequently.
4. CTRL+N / Command+N: New
You may already use this in Word to create new documents. But did you know that you can also use CTRL+N in your web browser to open a new window?
You can also use CTRL+N in your Windows Explorer to create a new folder for files.
5. CTRL+S / Command+S: Save
Raise your hand if you've ever lost unsaved work before.
A lot of programs now have auto-recovery built in, to recover any lost work if there's an unexpected crash in the program. But these are not without their faults. The auto-recover might not saved some of your most recent work, or might not work at all for some programs.
Save, save, save. If you have a short break in typing, do a quick CTRL+S to make sure you don't lose that work. Make it a habit, and you'll thank yourself later.
6. ALT+F4 / Command+Q: Close
Here's a rarely used one, but nonetheless helpful. If you have multiple applications open, and you're trying to quickly close them all. Simply enter ALT+F4 (or sometimes CTRL+W on a PC) in each one (make sure you have everything saved first before closing! See last point.)
7. TAB key: Move through a form
If you buy stuff online as much as I do, then you can probably relate to the slow, tortuous pain of moving through a lengthy credit card form. Same goes with booking airline tickets, filling out a survey, signing up for a service...pretty much anything that requires you input text into lots of fields online.
Fortunately, there's the TAB key, which allows you to move to the next field entry when filling out a form online.
8. TAB+Space: Submit a form
And when you reach the bottom of said form, there's probably going to be a "Send" button, "Submit" button, "Register" button, or "Next" button to move onto the next page.
If you TAB after the last text field, the button will become selected in your browser. Press the Space bar to "click" that button, and you'll have successfully filled out and submitted a form without touching your mouse.
I can't guarantee this works every time, but 60% of the time, it works every time.
Hopefully this helps you move through some of your applications quicker and allows to work more efficiently.
Of course, there may be other shortcuts that I missed...comment below if you feel there's another keyboard shortcut that makes your life easier that you want to share with the world.