When starting a company you frequently have to ask people for things -- introductions, advice, a meeting, sponsorship, money, etc. As you progress, you'll also have more and more people asking you to do favors for them.

Here's what I've learned about how to do this well:

Be concise.

Be nice and use pleasantries but not too many (if you're too obsequious or indirect it can be hard to figure out what you actually want).

Be appropriately selfish. It's ok to ask for things. It's ok to ask for things from someone who can help you more than you can help them right now. The startup community runs on people paying it forward. Just stay within reason, and don't ask people to do things that seriously puts their reputation on the line.

Always have a one sentence summary if you're passing something larger along (like a description of an event you want sponsorship for). You might think your three paragraph message is short, and it might be if the person you're emailing happens to get no other email. More likely she's got hundreds of messages in her inbox and your message feels anything but "short."

Be specific. Don't ask to meet for coffee or to be introduced to someone who can "help your startup." Those things are too vague. I might know someone who I'd be happy to introduce you to and who could really help your company, but the set of people I know is large, and if you're nonspecific in your request, you're offloading the effort to figure out who'd be helpful onto me.

Include the relevant details. If we're meeting, include your cell. If we're Skyping, include your username. Include specific days and times you're available; don't just say "I'm free whenever you are" (especially if that isn't true).

Remember: You can maximize your odds of getting what you want by minimizing the work the other person has to do to help you.