Mainly we people use Microsoft Word. With the help of shortcut key F7 you can easily find out you grammatical errors.
While word is great for catching spelling, nothing beats the old fashion way. If you have the time- and the document isn't too lengthy - try reading it backwards (EX: from the last word to the first). I do this all the time for my writers and am surprised by the simple mistakes that I catch.
I just use the spellcheck in Word, and update it with new words (like brand names I'm writing about) as I go. It does get annoying switching between US and UK spellchecking for different clients, but other than that I can't see a better technical solution - the only things Word's spellcheck won't pick up are if your typo is another correct word, and that's why you proof. Printing them out seems a big weird to me, but whatever works for you!
I use microsoft office when I write so I use their internal spell checker. I no longer go old school since I have grown to be comfortable using my PC. I just re-read what I did 2-4 times just to make sure nothing slipped by me. Also, in my attempt to be eco-friendly I am trying to do everything electronically.