Augustine said your subject line shouldn't exceed eight words, especially since mobile devices might cut off part the text.
Put the most important words right up front, and include any deadlines when relevant. If you know you need a response by a specific date, give yourself a cushion and ask for it a few days before the real deadline.
If you're emailing someone you've been introduced to by a mutual contact, include that contact's name in the subject line (e.g. "friend of John"). Or find something you have in common with the busy person, like a company you both worked for or a school you both graduated from (e.g. "fellow Harvard alum").
"Whenever you can find something in common, people are always more likely to warm up to you," she said. (Research on "similarity-attraction" backs her up.)
Augustine said that your email should ultimately highlight what you can do for the recipient, who might be inundated with tons of requests. Always ask yourself: "Why in the world should they bother reading this and actually responding?"
If you genuinely want that person's help or advice, and can't think of something you can offer in return, be very clear about what you need from them and what they can bring to the table.
In the case that you don't know the busy person, you should limit any introductory or background information. Don't include tons of hyperlinks in the text, either — those belong in your signature.
If you're emailing a busy person within your company, consult his calendar to see which time blocks are free. The person is more likely to be on top of his inbox during those times.
However, if you don't have access to the busy person's calendar, it's generally best to email him earlier in the week — but not too early. Augustine suggested Monday afternoon, Tuesday morning, or early Wednesday.
Most people are already spending Monday mornings trying to catch up on all the email they missed over the weekend; and they may be too checked out by Thursday or Friday to pay attention to your message.
If you gave the busy person a week to respond and you haven't heard anything from her after a few days, Augustine said you can ping that person politely — especially if she's a coworker or your partner on a project. She might simply have missed the message.
However, if the busy person is someone outside your company whose advice or assistance you requested, you obviously can't set a deadline in your original email. Instead, you can say something like, "If I don't hear from you in a week, I'll follow up" and then do so.
Something as straightforward as, "I want to make sure you saw this; please let me know if you'd like to get together" should suffice.
