To make your reading passes effective, give each of them a clear focus. Rather than trying to read the text once and thinking, “Is everything all right?”, make the second read specifically about things like spelling, punctuation, repeated words, or consistency in the document. This makes the task easier and smaller, so that you’re less likely to miss mistakes. The problem is to keep the separate passes straight so that they aren’t jumbled, redundant, or forgotten.
Have a copy to edit that is clean and decide how you will mark it. In a word-processed version of the text, use Track Changes for certain fixes and leave comments for questions. On a physical proof, use your chosen correction marks, and note queries in the margin. Don’t mix the two in mid-document; pick one, and be consistent throughout. If you do this, you’ll remember which things you’ve corrected, you won’t go over the same mistakes again in each reading, and you won’t forget to note something that should be marked.
You might start with surface errors (spelling, typos, omitted or repeated words, doubled spaces). Read carefully using an empty sheet or an on-screen scrolling aid to highlight your current line. Don’t get bogged down with sentence reordering or spelling questions; mark only the things that fit that particular pass. Other questions can be marked separately or ignored for now, to be addressed later.
Next you could focus on punctuation and some grammar issues; then another pass could be all about consistency. If you have a consistency checklist, add to it. If you notice how you spelled out a proper name or abbreviation, or whether you chose one spelling or another, or if you capitalized or hyphenated something, or how you wrote out a date or number, put that on a separate sheet to consult. If you come across the same item later, use the notes you made rather than guessing whether you’re doing it the same way, to avoid the mistakes in the earlier sections.
Beginners tend to lose track because they mark and correct as they proceed; then they forget whether or not they’ve reviewed the previous sections. A small checkmark solves a lot of that problem. After you’ve read and corrected a full page (or even a few paragraphs), you could write a short note to mark that it’s done. Or, if you have a checklist, you can tick it off. The very next thing that you’d do is to review the earlier changes (accept or reject them) before starting another pass or read. Save another copy of the revised text. Check that all questions that needed to be asked have been recorded as comments.
To test yourself, select about two hundred words that contains many different kinds of errors. Make one reading pass for spelling and spaces, another for punctuation, and another for things like consistent capitalization and the double use of words and terms. After each pass you can record what you found and how many things you’re not sure about. Then compare your corrections with the clean version of the text, looking specifically at whether you fixed something that made you create an error in the spacing or the punctuation or the word.
Then you should read the text one final time, the clean version without having to look at the corrections or anything else from your earlier readings. Check headers, endings of sentences, spaces, corrected things. The individual passes are how you concentrate, but it takes another reading of the whole thing to know that your text is a complete proof; the proof is the collection of everything you’ve read, corrected, and reread.