We all know that using a spellchecker isn’t sufficient.  This poem by Anonymous really brings it home:

Eye halve a spelling chequer
It came with my pea sea
It plain lee marques four my revue
Miss steaks eye kin knot sea.

Eye strike a key and type a word
And weight four it two say
Weather eye am wrong oar write
It shows me strait a weigh.

As soon as a mist ache is maid
It nose bee fore two long
And eye can put the error rite
Its rare lea ever wrong.

Eye ran this poem threw it
I’m shore your pleased two no
Its letter perfect awl the weigh
My chequer tolled me sew.

-Sauce unknown

"One is the downside of our brain’s highly developed “autocorrect” function. Dropped and extraneous words are frequently overlooked, because we automatically ‘see’ what we think we should be seeing. Some editors have tricks to try to overcome this tendency, such as proofreading with all but one line of type covered at a time. This forces you to slow down and see what’s really there, not what your brain expects to find."

To increase my chances of finding my own errors, I generally:

1. Avoid proofreading immediately after I’ve finished a translation
2. Look at those segments first I translated at the end of the day
3. Print out a copy if I think I need a “fresh” look at things
4. Proofread in the morning when my brain hasn’t already been bombarded with thousands of words

What I haven’t tried yet but will is using a Text-to-Speech program, such as TextAloud by NextUp http://www.nextup.com/TextAloud/ Perhaps someone has had some experience they would like to share?