Demand rent only
A pay-or-quit under CCP § 1161(2) should state the unpaid rent that is actually due. Late fees and other charges usually do not belong in the same demand. Overstating the amount is a classic reason a later unlawful detainer is thrown out.
Count business days, not calendar days
Since SB 385, the three days are court business days. Weekends and judicial holidays do not count. Start the clock the day after valid service, not the day you printed the notice. Put the due date on the face of the document so the tenant — and later the court — can reconstruct the math.
Serve the way CCP § 1162 allows
Personal service; substituted service on a person of suitable age plus mailing; or posting and mailing when those fail. Keep a proof-of-service affidavit that matches what you actually did. Informal texts or a notice taped once without mailing do not finish the statute.
If they pay, stop
Full payment inside the window satisfies the notice. You cannot keep the same notice alive for a later filing. If they do not pay, the notice and proof of service travel with the unlawful detainer — they are exhibits, not the lawsuit itself.