I find myself typing the same thing over and over again when I engage customers and vendors in email dialogue. To help avoid this time consuming task, I have started writing my ideas in templates and simply pasting them into my conversations with people.
I've heard that there are computer programs that let you do this (dedicated clipboards, for example, that store dozens of items) but I didn't feel like searching through tucows.com for a free download so I just use a couple of very basic notepad files in a folder with the phrases in them. It's not perfect, some might point out, but it works for me and that's the most important thing.
All I do is open the file and copy and paste the phrase I'm looking for.
Now, if you're thinking that I simply send out form letters, I don't and I don't recommend it. Instead, I find that I periodically include a paragraph in my emails and I ALWAYS proofread my emails to make sure that my “boilerplate” paragraph makes sense and is integrated into the email.