Here's the list of words and/or patterns that I use…
A (as a single letter, either 'a' or 'i'. If there's no single letter at the beginning of the sentence, or after periods or commas, the 'a' will most often be correct)
I (occurs most often at the beginning of sentences, or after commas, though not necessarily)
*A note on the letters A & I: If you come across a single letter right before an apostraphe, it will most definately be an I, where the words "i'm", "i'd", etc will be found. Also, if your puzzle contains this and an different single letter, you've got a start that can't be anything else, or so my experience tells me.
That (the pattern with the 't' beginning and after is almost a dead give-away, but keep in mind there are other words that fit the same pattern. Can almost definitely be confirmed if you find a 3-letter word that has the same 2 letters at the beginning, thus the word 'the')
People (I don't usually spot this one as easily as the others, but notice the positions of the 'p' and the 'e' along with the other two letters)
Little (notice the patterns in the 'l', the 't', and the extraneous letters 'i' and 'e')
I know this list is short, and although I do know of more, I just do it so naturally that I don't realize it. I'll add more words and stuff as soon as I come across them.