Typing.

If you aren't touch-typing and are looking down at the keyboard, or even just having to spend mental cycles thinking about typing, it's taking away from your capacity to think about the problem you're solving.

Can you write programs without being able to type? Sure, of course. But, you asked for basic skills that will improve your programming, so I say: typing.

60 WPM is a minimum. 80-90 WPM is a reasonable low goal. 100-120 WPM is probably an upper bound limit on QWERTY; if you're very serious, you may want to consider learning Dvorak or Colemak layouts, where you might be able to hit top speeds of 150-200 WPM.