This is a question that comes up often, especially from newbies...
"I have heard that you should NEVER use ly adverbs (or choose your poison...tags besides asked and said, flashbacks, dream scenes, mirrors...). Every time I think something works, someone tells me I shouldn't do it. Am I screwing up? Is my manuscript going to get laughed out of the slush pile?"
First of all, even clichés work when they are the best fit for what you need to accomplish. If your gut instinct says it works, go for it. If one crit partner says it's not working, look at it again but follow your gut. If three say it, seriously consider that it might need changed.
Flashbacks should be used SPARINGLY, because they interrupt the forward flow of the novel. HOWEVER, sometimes...like in the case of Stephen King's IT, the novel is based on the intrusions of past memories into minds that don't recall what happened in the past but need the information to effectively fight in the current timeline. If you have a reason that flashbacks have to happen and can do it skillfully, do flashbacks more than sparingly. Many editors don't want to see more than a few flashbacks, otherwise.
If the descriptive tag or ly adverb does the job best, use it. If not, you are cheating yourself and your reader by either "telling" and not "showing" or by not using a descriptive and active verb when you might do so.
Saying they all suck isn't right. Saying you should never do it isn't right. Saying you're going to have a problem finding an editor/agent that will sign it, if you overdo it is correct. It doesn't mean you CAN'T do it and do it well. It means it's going to be harder to sell it. NOT impossible. Harder. There is no absolute in this business. Trust me.
Listen to that inner voice. Ninety percent of the time, when you hear someone say "NEVER do..." what they really mean is "Don't do too much..." No, don't change everything to fit those natty rules. I certainly don't, and people like my stuff, too. If it works, let it stand. If the editor doesn't like it, he'll/she'll tell you.
There are three unbreakable rules about writing, and no one knows what they are. The fact is, every editor has his/her own version of "the rules." The main thing is not to overdo any of the tricks in your bag, unless you do it well. Grinning... I love that part. For most writers, that means you really shouldn't overdo anything. Don't worry about breaking a few rules, as long as you do it well. Go ahead and submit; it's unlikely you're going to get laughed out of the slush pile for it, as long as it's done well.
ONE rule never to break is the one about following the individual guidelines for the editor/agent you're submitting to. If they say 12 pt Times New Roman, 1" around, double spaced, indent .5 for paragraphs, you do it! If they say 10pt Courier, 1.5" top and 1" around, 1.5 space, .3 for paragraphs, straight quotes, you do that.
If they say 80-100K, you can range up to ten percent out of that without querying to ask...IOW, as low as 72K and as high as 110K without asking. You CAN ask to range further. NEVER apologize that you're not in the range, but ask them if they would consider longer/shorter. The worst they can say is 'no.'
The other rule never to break is to act professionally with the professionals out there. Grinning... Know what the terms mean and use them right. If they ask for cover letter, don't send a query letter. If they ask for outline, don't send synopsis. Don't use IM speak with them. Don't play the diva.
Beyond that, if it works, try it. You might have a longer road ahead of you selling it, but nothing is impossible, even if you aren't selling it to your first choice or your third.
There is a wives' tale among writers that being famous means you get to break all the rules with impunity. That is not true, IMO.
The "master writer" is the one who can break the rules so successfully as to be allowed to break them with no repercussions. Example time? There are those who became "famous" but not masterful, who broke the rules in a way that was not masterful at that point, and who were stomped for it, because it was not done masterfully. In order to break the rules and have no repercussions, IMO, you must do so masterfully, and as such...you must be a master of the word, if not famous yet for your skill. Fame can come on either side of that equation...or perhaps never at all, though the artist/creator is still a master of the word. Make sense?
Others will state that you get to break all the rules, if you are a publisher. I disagree. You may be able to get it published, but that doesn't mean you won't get stomped by readers and reviewers for it. I maintain that not doing it masterfully means there are repercussions somewhere.