When you look at your stack of critiques and you know something is wrong and you wholly agree with the critter, just change it. Don't sigh. Don't wait for more critiques to compare it to. Don't ponder if you'll even keep the sentence when you make your big edit. Just grab your draft and change it.
It's like having a side of peas with your chicken. You know you have to carve it, but if you eat a pea here and there, you'll do a little less scooping later. For some people, especially beginners to editing, this is a useful exercise in getting into the editing mindset and gives you one less thing to drag your feet about later.
About 80% of all quick fixes are grammar-related.
Here's a short list of some repairs that take little to no time to complete:
Typos,
missing or incorrect punctuation,
sentence needs to be broken into two or combined into one,
sentence needs a re-write to be less confusing,
wrong word,
odd word choice,
misspelling,
incorrect verb conjugation,
wrong pronoun,
passive to active voice,
past to present,
etc.
As you can probably tell, this guide is designed for writing posted on websites and forums, so I want to stress the importance of making some changes immediately.
If your story is the kind that's posted somewhere, and as you continue to write it or edit it, it's still available for comments and critiques, seriously consider making quick fixes right away.
Here's why:
Having people agree that you made the same mistake can be wonderful. It'll make you a little more confident that there is a problem there, and that more than one person sees it (which can make you feel like you're changing it for the better, instead of for the individual).
BUT
One of the best ways to improve is to do everything to the best of your ability. That way, when people come in and offer their input, you aren't rolling you eyes and going "I know, I know."
Think of it this way. Your mom comes into your room and tells you that you need to dust. You know you need to dust. Dad says the same thing. And Aunt Sue, and your sister, and your little cousin.
Instead of getting new, unique comments from Dad, Aunt Sue, your sister, and your cousin, you just get more of the same and it doesn't help you because you already know it.
Comments can be hard to come by. Do you really want to waste them all on the same issues?
If everyone's flagging the same mistake, they might not catch something else.
In my experience, issues such as bad grammar can detract from the critique process. Instead of enjoying the story more, or being able to pick up on plot issues or sentence structure or voice, if I'm stuck in a sea of typos and misspellings, I might be too tired or completely miss an underlying issue.