I just started to learn Objective C and here are some Xcode 5 shortcuts that I find useful when just getting started with the Editor.
Move cursor back and forth one word.
Shift + Option + Left/Right arrow
Move cursor up and down one line.
Shift + Option + Up/Down arrow
Delete current line where the cursor is located.
Control + k
Open new tab.
Command + T
Close tab.
Command + W
Switch to left or right tab.
Shift + Command + { or }
Open existing file.
Shift + Command + O
Switch between .m and .h file.
Control + Command + Up/Down arrow keys
Run or Build the app
Command + R
Show/Hide Project Navigator
Command + 0