Don't BIF people during off-hours. "BIF" stands for "before I forget" and refers to emails sent on evenings or weekends out of fear of forgetting a to-do or follow-up. This sets a mutual expectation of 24/7 work hours and causes a plethora of problems. There are a number of better alternatives. First, use a service like Jott.com instead that allows you to send voice reminders via cell, which are transcribed and sent to your inbox or someone else's. If to someone else's, be sure to add "no need to respond until [next work hours]." Second, if you prefer low-tech, externalize follow-ups and to-do's in a small notebook like a Moleskine instead of entering the "bet you can't eat just one" inbox.
Before writing an email, ask yourself: "what problem am I trying to solve?" or "what is my ideal outcome?" Unclear purpose, usually a symptom of striving to be busy instead of productive, just requires later clarification from all parties and multiplies back-and-forth volume. Be clear in desired results or don't hit that Send button.
Learn to make suggestions instead of asking questions. Stop asking for suggestions or solutions and start proposing them. Begin with the small things. Rather than asking when someone would like to meet next week, propose your ideal times and second choices. If someone asks, "Where should we eat?", "What movie should we watch?", "What should we do tonight?", or anything similar, do not reflect it back with "Well, what/when/where do you want to...?" Offer a solution. Stop the back and forth and make a decision. Practice this in both personal and professional environments. Here are a few lines that help (my favorites are the first and last):
"Can I make a suggestion?" "I propose..." "I'd like to propose..." "I suggest that... what do you think?" "Let's try... and then try something else if that doesn't work."