Reply in the thread, or start a new one on purpose. When an email follows up on the last one, send it as a reply, so the earlier message sits below it and the reader has the context. When you change the angle, such as an offer or a last email, start a new thread with its own subject line.
Add something new each time. Give an example, a resource, or a direct question. “Just checking in” gives the reader no reason to reply.
Keep it short. Most follow-ups need three to five sentences and one question.
Make the reply easy. Ask a question they can answer in one line, or give them options to choose from.
Know when to stop. End with a polite email that closes the loop and leaves the door open.