Proof reading is about checking the Spelling, Grammar and Punctuation.
We start by looking at individual words – are they spelled correctly. Then is the sentence a fragment, (Groups of words that look like a sentence but structurally aren’t). Next, does it have proper punctuation, use of colon, semi-colon, missing or redundant commas. Is it grammatically correct?
Many of these items can be picked up by a word processor, however, they cannot cope with the human element of interpreting the intention and often miss simple word swaps like bear and bare. (Word lets you get away with “Bear in mind that we are going our later”).
It’s a good idea to have a proof read once your document is complete and after the editing phase. Once editing is done, it’s a good idea to repeat the process to remove any new issues that may have been introduced before publishing.