I omit "to" and "for". Doing so reduces the number of words in the readback. All headings and FL clearances are "fly to" instructions, never "fly from". Hence there's no point in stating the obvious...
Whenever numbers are said on the radio I'm very careful to use the appropriate prefix such as "heading", "altitude", "FL" or callsign. Just saying the numbers I find very unprofessional such as: cleared 180, 270, 551.
/LnS