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Another thing which might be useful when typing equations (here or anywhere on a PC) is the use of "Alt codes". Frank has provided convenient buttons to insert a degree symbol (°) and interpunct/bullet (·) when composing a message, the latter of which could also be used as a "multiplication dot". But, one can insert other symbols by simply holding the "Alt" key and typing a one to three digit number on the numberpad. For example, Alt+246 produces the "÷" symbol. Not every symbol is available using these codes, but some of the most commonly used ones are. At the very least, they can save you some keystrokes. Four keystrokes produces "÷", as opposed to ten for "divided by". A more extreme example would be that instead of typing out that "dip is approximately equal to the square root of the height of eye in feet", one could simply type "dip ≈ √(height of eye in feet)"...saving 36 keystrokes (≈ 50%).

I have attached a pdf of the three digit codes (minus those readily available as keys on a standard English keyboard). This can be printed, cut out and kept handy near one's PC for reference.