Up/Down Arrow Keys: Select a result

Right Arrow or Slash: Show item contents. Use the Option key to show an alternate contents (Invisible files, Package Contents)

Left Arrow or Shift-Slash: Show item parent.

Escape Return to normal search mode.

Showing an item's contents or parent will turn on browsing mode. Anything you type in this mode will search only the current directory, and not the full catalog.

Holding down the last key typed (key repeat) will cause the command to be submitted. Typing command-shift with a letter will match that letter to an action and automatically execute the command. (So with a file selected, command-shift-R will cause a reveal)