How do you give two weeks' notice?

Tell your manager first, live, in a meeting or call, before colleagues, before LinkedIn, before the group chat. Managers forgive almost anything except learning secondhand. Keep the conversation short and warm: you have accepted another opportunity, your last day is X, you will make the transition smooth.

Then send the letter, which is a formality for HR's file, not an essay. Three sentences: you are resigning from your role, your final day is the date, thank you for the opportunity. No reasons, no feedback, no grievances. Anything critical you want heard belongs in a spoken exit interview, if anywhere, because the letter is permanent and your future references are not.

Two weeks is convention, not law; nearly all US employment is at-will. Some companies walk resigning employees out same-day, particularly in sales, so have personal files off the laptop before the meeting. Then finish strong; the last two weeks are the reference.