Here are some tricks that you can use almost everyday:
alt + tab -> switch between tasks without the click of a mouse button.
windows + D -> Show Desktop.
windows + R -> opens the run window.
windows + E -> opens windows explorer.
ctrl + backspace -> delete an entire word behind the cursor.
ctrl + shift + T -> accidentally closed a tab? This trick will reopen the most recently closed tab.
ctrl + T -> open a new tab.
ctrl + W -> close current tab.
ctrl + shift + N -> To open Google Chrome in Incognito mode.
ctrl + shift + R -> clear cache.
ctrl + D -> add bookmarks.
ctrl + shift + D -> bookmark all open tabs.
ctrl + +/- -> Increase/Decrease text size.
c -> compose a new email
r -> reply to an email.
f -> forward the email.
n -> move to the next message.
p -> move to the previous message.
OneTab -> a Google Chrome extension that stores all your open tabs in a single tab. Saves RAM usage and saves YOU from getting lost in the gazillion tabs that were open.
F2 -> Rename a file without using right-click.
ctrl + F -> find a word in a document/web-page.
Snipping tool -> to capture part of a screen.
Task Manager -> monitor the open tasks, processes, RAM usage and end tasks that are not responding.
Note: Most of the tricks are mentioned for Google Chrome and Windows OS, some may work on Mac OS as well by replacing ctrl with cmd. Will certainly keep adding if I happen to use some more.