Closings
I've had a few questions in seminars lately about appropriate closings. The standard professional closing is "Sincerely" but most people feel uncomfortable with that, which has led to the overuse of "Thanks".
I've seen "Respectfully," "Best wishes," "All the best," "Best," and "Cheers" (which seems to be a particular favorite of older men with a propensity for daytime drinking). Some old school closings that have certainly fallen out of fashion are things like "Yours" or "Yours truly," which I would reserve for personal relationships. I have a former student who has elected to use "With enthusiasm," which I like, but he is truly an exceptionally enthusiastic person, so it has veracity for him.
What prompted me to respond to this topic were some recent international emails, particularly with Spanish speakers in various countries. Here are some of the (translated) closings they have used:
Without further details, I say goodbye to you
Receive a cordial greeting
Keep in touch
With respect
Attentively
Greetings
These are a bit more formal, but convey a variety that I don't think we have and a real attention to the purpose of the closing, which is to describe how you are feeling toward your audience. I think the more we consider closing as part of the tone, the better our closing words and phrases will be. For the most part, they are used to describe your attitude (usually using an adverb like an -ly word or a phrase using "with") about the content of the message or the audience.
Play around with some closing words or phrases and see what feels the most comfortable for you.