My #1 utilized software tool is email. A few years back I checked the stats for the last year for my work and personal email combined: I received and read on average 397 emails a week, and sent 358 emails a week that year (this excludes the email which is spam or which I have auto-filters to file to certain folders -- these are real emails I read, write and process).
Over the years I've adopted some best practices to process and write email -- I hope you find some of them useful.
4 Rules of Processing Email
When you get an email, do one of four things immediately:
Do it (If it takes < 2 minutes)
Delete it (If you are done with it)
Delegate it (If you can forward to another for completion)
Defer it (But have some way to remind you the email needs actions -- maybe file it to a 'Tomorrow' folder, flag it, etc. If you're defering it, email them to tell them that you'll get to it later.)
Using this system avoids the '1,000 emails in my inbox' situation, and prevents you from scanning the same email a dozen times before acting on it, which wastes time.
3 Rules of Addressing Email
Never "Reply All". Well, not unless you absolutely must.
BCC Groups When Needed. If you're sending email to a group where a "reply all" will be troublesome, send the email to yourself, and BCC the group, thus disabling the "reply all" capability. You can mention in the body who you sent it to if necessary.
Don't Enter Recipients Till You're Done. Don't enter the recipients email address in the 'To' box until you're done composing it -- this prevents the premature sending of email by mistake. If you need to, list the recipients at the top of the email body as a placeholder, then remove that and fill in the 'To' box at the end.
8 Rules of Composing Email
When composing email, do the following:
Be Concise (also known as the 'Don't make me scroll!' rule). If the email is so long the reader will have to scroll to read it, it is too long. Here's how you make it 'shorter' -- create an executive summary (maybe labelled 'Summary') at the top, then put the larger section beneath labelled 'details'. This frees up your reader to scan the summary and only read the details if/when they need to.
Use Multiple Emails For Multiple Topics. If there is more than one topic, break it into multiple emails. Otherwise the read may respond to one topic and ignore the other.
Communicate "Action Steps." List the action steps first, not last, in the body of the email, so the reader can know within seconds what is expected of them.
Number Your Questions. This makes it easier to respond to and clears up confusion about what point the author is referring to.
Include Deadlines. List deadlines even if they are artitrary (otherwise, they may not get done this year!).
Tag Subject Lines With Priority and Deadlines. Listing "JUST FYI:", "URGENT:" or "ACTION REQUIRED:" or "NEEDED BY 12/6:" at the beginning of a subject line saves time and increases the odds it will get the attention it deserves in the timeline desires. In particular, use "FYI" for emails that have no actionable information. Maybe add "Just FYI" in the body as a second tag.
Make Subject Lines Informative. An email which says "ACTION NEEDED BY COB 3/12: Please review ARCW contract" in the subject line is much better than one that reads simply "Contract" or "Re: ARCW".
Never Send an Angry or Contentious Email. Pick up the phone or schedule an in-person meeting if that's the tone of topic.