Most people either follow up too apologetically, which invites the delay to continue, or too pointedly, which makes the other person defensive before they've even read the ask again.
The apologetic version, "sorry to bug you again, I know you're busy, just wanted to circle back whenever you get a chance", sends a quiet signal that the request isn't actually that important, which gives the recipient permission to keep deprioritizing it. The pointed version, "just following up on this, as I mentioned last week", reads as a small rebuke, even when that's not the intent, and tends to put people on the defensive instead of prompting action.
A good follow-up doesn't apologize for existing, and it doesn't scold. It just restates the ask, cleanly, and makes it easy to act on right now.
The version that actually works has three parts: restate the specific ask so the person doesn't have to scroll back to find it, add any new information that's changed since the original message, and give a real reason for the timing if there is one. That's it, no apology, no guilt, no passive-aggressive undertone.
"Following up on the budget sign-off from Tuesday, I need it by end of day tomorrow to keep the vendor contract on schedule. Let me know if you need anything else from me to make the call."
That message does its job in three sentences: it's specific about what's needed, it explains why the timing matters, and it offers to remove any blocker on the recipient's side. Nobody reading it feels nagged, because there's nothing in it beyond the facts and a genuine offer to help.
Timing the follow-up itself matters as much as the wording. Following up too soon, within a day of the original ask, reads as impatient and can actually slow things down, because it signals you don't trust the other person to manage their own queue. Waiting too long lets the ask go cold entirely, and by the time you do follow up, the original context is gone for both of you. A rough rule: match the follow-up window to the urgency you stated the first time. If you said "by Friday," a follow-up on Thursday afternoon is fair. If you said "whenever you get a chance," following up two days later isn't.
If a second follow-up is needed after the first goes unanswered, that's usually the signal to change the channel rather than repeat the same message, move from email to a direct message, or from a message to a quick verbal check-in. Repeating the identical written ask a third time tends to read as pressure rather than persistence.