This has nothing to do with being frugal or living "green", but I swear it's the best tip I've ever received regarding work stuff. Someone in IT gave me this tip back in 2002 when I worked for the House of Representatives, and it's still applicable today.
If you're in a position at work where you respond to many of the same emails throughout the say (signing up for events, sending invoices, etc., etc.,) THIS is the tip for you. Many people who send the same email day in and day out, keep the template for that email in a separate Word document. No longer my friends, no longer.
In Outlook, find where "Signatures" are stored. Typically they're under Tools and Mail Options. Select "create new" signature and copy and paste your template response in to a new signature. Leave blanks or "x" if you need to fill in personalized data later (names, time, date, etc.,).
The next time you get an email pertaining to this topic, rather than open a Word document and copy and paste, simply hit "reply" and then select the appropriate signature. It will populate right in the body of the email. Voila.
I once attended a global training for my last company in Spain. There were about 40 of us recruiters there for a 3 day training. Somehow this tip came up and within minutes, I was leading a training on how to do it. The feedback the event organizers received was that in the whole 3 days of training, my signature tip was the most useful. Go me.