Tabs and Windows

Function Shortcut
New Tab + T
Close Tab or Window + W (same as many mac apps)
Go to Tab + Number Key (ie: ⌘2 is 2nd tab)
Go to Split Pane by Direction + Option + Arrow Key
Cycle iTerm Windows + backtick (true of all mac apps and works with desktops/mission control)
Splitting
Split Window Vertically (same profile) + D
Split Window Horizontally (same profile) + Shift + D (mnemonic: shift is a wide horizontal key)
Moving
Move a pane with the mouse + Alt + Shift and then drag the pane from anywhere
Fullscreen
Fullscreen + Enter
Maximize a pane + Shift + Enter (use with fullscreen to temp fullscreen a pane!)
Resize Pane Ctrl + + Arrow (given you haven't mapped this to something else)
Less Often Used By Me
Go to Split Pane by Order of Use + ] , + [
Split Window Horizontally (new profile) Option + + H
Split Window Vertically (new profile) Option + + V
Previous Tab + Left Arrow (I usually move by tab number)
Next Tab + Right Arrow
Go to Window + Option + Number

My Favorite Shell Key Combos

These might be helpful to getting you faster with the shell but really this isn't iTerm2 specific. I'm assuming you are using bash or zsh on Mac. There are many tips but I use these quite a bit. There is also more than one way to do it sometimes so adopt what you like best.

Hopefully some of these change your life. :)

Function Shortcut Use
Delete to start of line (favorite) Ctrl + U Use this to start over typing without hitting Ctrl-C
Delete to end of line (favorite) Ctrl + K Use this with command history to repeat commands and changing one thing at the end!
Repeat last command Ctrl + Up Arrow Cycle and browse your history with up and down. Ctrl-R is faster if you know the string you are looking for.
Move back and forth on a line Arrow Keys This takes you off the home row but it's easy to remember
Move back and forth on a line by words Ctrl + Arrow Keys Fast way to jump to a word to correct a typo or "run again" with minor changes
Delete previous word (in shell) Ctrl + W It's faster to delete by words. Especially when your last command was wrong by a single typo or something.
Clear screen Ctrl + L This is telling the shell to do it. When this doesn't work + K will tell iTerm to do it which works when you aren't in a shell. Use this instead of typing clear over and over.

Moving Faster

A lot of shell shortcuts work in iterm and it's good to learn these because arrow keys, home/end keys and Mac equivalents don't always work. For example + Left Arrow is usually the same as Home (go to beginning of current line) but that doesn't work in the shell. Home works in many apps but it takes you away from the home row.

Function Shortcut
Move to the start of line Ctrl + A or Home
Move to the end of line Ctrl + E or End
Move forward a word Option + F
Move backward a word Option + B
Set Mark + M
Jump to Mark + J
Moving by word on a line (this is a shell thing but passes through fine) Ctrl + Left/Right Arrow
Cursor Jump with Mouse (shell and vim - might depend on config) Option + Left Click

Copy and Paste with iTerm without using the mouse

I don't use this feature too much.

Function Shortcut
Enter Copy Mode Shift + + C
Enter Character Selection Mode in Copy Mode Ctrl + V
Move cursor in Copy Mode HJKL vim motions or arrow keys
Copy text in Copy Mode Ctrl + K

Copy actions goes into the normal system clipboard which you can paste like normal.

Search the Command History

Function Shortcut
Search as you type Ctrl + R and type the search term; Repeat Ctrl + R to loop through result
Search the last remembered search term Ctrl + R twice
End the search at current history entry Ctrl + Y
Cancel the search and restore original line Ctrl + G

Misc

Function Shortcut
Clear the screen/pane (when Ctrl + L won't work) + K (I use this all the time)
Broadcast command to all panes in window (nice when needed!) + Alt + I (again to toggle)
Find Cursor + / or use a theme or cursor shape that is easy to see