I've been thinking about best practices for password reset emails lately. Instead of trying to re-invent a wheel that other folks have already capably designed, I'll just highlight a couple of thoughts and link to some more detailed info from a couple of folks with have good insight to share.
The most important thing to remember, I think, might be this: Always reset, never remind. Meaning, don't email a password to the user. It could spit out the password to the wrong person, if abused. Also, aren't your passwords one-way encrypted? Don't store it in the clear, don't send it out in the clear.
A close second: Make sure your emails don't look like phishing. Everything should properly authenticate with SPF and DKIM. Your domain should have a DMARC policy in place. Lock that domain down, to make it harder for faked password resets (or other notifications) to get through to the inbox.
And finally, delivery speed really matters -- though busy email systems can often still deliver emails pretty quickly, you will find that delivery delays due to poor reputation will absolutely kill you here. This highlights why you need to keep your nose clean with your marketing emails -- so your reputation is stellar enough that the same communication channel is open and available to you for very quick delivery of very important user notifications, like password reset emails.
AOL, Yahoo, Gmail (and possibly other ISPs) seem to delay delivery of inbound email when a sender's reputation is only so-so. And you can't always try to segregate that mail to work around the issue. You might not have enough transactional mail volume to warrant a dedicated IP address just for notifications. And your domain name is going to be the same across all types of email, assuming you want to stick solidly to your primary brand and its domain.
Microsoft's Troy Hunt has put together an excellent number of suggestions on the topic of resetting your password, and Postmark's Garrett Dimon dives deeper into the email side of this equation. They're both worth reading.