People like responding to messages that are personalized and relevant.
If you tell them something useful, they are more likely to reciprocate and listen to what you have to say or offer.
Know when to send multiple reminder emails and when to send a single one then let it rest. Journalists are usually bombarded by messages so sending several reminder emails can be fine if you have a compelling story. Conversely, a distant professional acquaintance is only acceptable for up to 1 or 2 reminders at most.