This year I made a pledge to myself and my staff (since most of my email comes from them) that I will answer all emails within 24 hours. The trick for me has been ignore my flood of email during the day. I average about 50-80 incoming emails each day. During the last hour of my work day, I take my account offline (so I don’t get replies back as I’m replying) and answer them all, then send them out in one batch. The tradeoff is that people need to call me or IM me if they need a response right away, but this was already the case since some days I would not check my email until the afternoon anyway. (My day is usually full of back-to-back meetings with staff.) Resisting the temptation to check email during the day has also allowed me to be more present at meetings, since I’m not trying to sneak in an email or two between each person. I learned this trick from watching my property manager when I was in the process of securing a rental apartment from him. Whenever I emailed him, I would always get a response between 4-5PM.
This blog post by Michael Hyatt talks about this technique and others.