Good advice is a free gift that's also priceless. Good advice can save your life. Good advice for writers, while likely not life-saving can be massively time-saving and easily sanity-saving. In fact, my writing career was launched in earnest because of one very good piece of advice*. Bad advice is an albatross around your neck. So how do you know which is which?
There's no way to know, of course. At best you go off gut feeling. As a writer this is almost always right. After all, your gut feeling is just advice as given to you by your subconscious. It's that good advice that kept your ancestors alive long enough to make you. Think about that for a second. There's a whole lot of not getting eaten by sabre-tooths and drowning in too quick waters in your past. All because of that advice. The people that listened to bad advice 'Let's check out that dark cave! It looks neat!' got eaten.
So the stakes aren't that high here, but as mentioned before, bad advice can really ruin a work of yours or even worse make you put down the pen. Here's some tips to know if it's bad advice.
- If the person doesn't write don't take non-style, non-critique advice very seriously. By that I mean, take their advice on plot ('I didn't understand what happened here', or 'the main character's voice got weak there' ) and substance, but devalue general advice. Let me give you an example. I once had someone tell me that I should 'write what I know', because I was not, nor had ever been a cop. They didn't say 'needs more authentic detail' or 'this character sounds like a cliche' (both vaild critiques), she basically told me I shouldn't write**. I ignored her and that book has an agent now.
- If the person is a writer but doesn't write in your style, take their advice carefully. Advice about getting a publisher, or editing your work is probably valid. Advice on your style is probably not, no matter how much better a writer they are. This isn't a personal thing, it's a unique voice thing. Here's my example. I do not Like the writing of George R.R. Martin. I know he is an excellent writer and I love the HBO show. But I find him proscriptive, overly wordy and, for me, he describes his world so thoroughly that there's no room in it for me. Anne Rice is the same. I feel like somewhere in that 1,000 page book a 250 page screamer is dying to get out. Now clearly a LOT of people disagree with me. And since art is subjective, they are 100% right. My advice to George R.R. Martin would be to edit the ever loving shit out of his books and I'd probably enjoy them more. But this would be wrong and would be terrible advice. His advice to me would likely be equally bad.
So, I hope that helps. Remember the best advice you can get is from someone who likes what you do and/or likes the style or milieu you've chosen to write in. If not, don't disregard the good intentions of others, just weigh it against the mitigating factors and hopefully you can separate the good from the bad and just plain ugly advice.
*I was told I had the knack as a writer but above all else I needed to read more. It was so very, very true.
** I'm going to do a separate post on the absolute stupidity of 'Write what you know' as a concept. It's one of the most destructive fallacies in fiction writing.