I especially agree with the first tip about a cold email's goal being to pique enough interest to get a positive reply. The goal is not to convince someone to write a check on the spot by writing a 10-page email -- that's an unattainable goal and no one is going to read a cold email that long.
To use an analogy, a cold email should be like a movie trailer -- or even a movie poster. A movie poster doesn't give you a long summary of a movie, but it gives you enough info to decide if you might be interested. (I wrote a little about this analogy a few years ago: https://www.codingvc.com/what-movies-can-teach-you-about-pit...). A good rule of thumb is to list ~3 bullet points that you think make your company stand out the most. These could be about the team, the product, the traction, or anything else.
It's also good idea to mention your company's stage. Lots of emails don't mention what round they are trying to raise or how far along a company is, and most investors operate in a narrow band. Roughly speaking, pre-seed investors are a fit for <=$1.5m, seed for $1.5m-$4m, and Series A beyond that.
If you send emails from your startup's email address and use LinkedIn, add the email address to your LinkedIn profile so that people can search by it. If your name is not unique and your company name isn't in your LinkedIn profile, people won't be able to look up your background and experience.
Finally, light personalization helps, faux personalization hurts. Light personalization could be a sentence like "It looks like we both went to Dartmouth!" (human connection) or "I saw you invested in companies A and B, which help accountants and lawyers bring their paperwork online. Our company is helping auditors bring their paperwork online." (shows effort/research). Faux personalization is stuff like "I did some research and based on your investment thesis I think you'd be a great fit" (intentionally vague and can be sent to every investor) or "I see you invested in MediaStartupA and SaaSStartupB, so I think you'd really like my RoboticsStartup" (name-drops startups, but the startups are random and completely unrelated).
FWIW most of these tips are not specific to emailing investors, and they can apply to cold emailing anyone.