Writing is one of those professions that sometimes, like Rodney Dangerfield, get no respect.
And sometimes it's the writer's fault.
I have participated in many an online forum for writers and attended numerous book events, sometimes as the author, but most of the time as a member of the audience (let me add to that: mainly as an author, trying to learn about writing and being a professional writer.) And in the process, I've been privileged (?) to witness a few things that became indelibly etched in my mind as key steps to being a professional.
First off, and this is most often seen in anonymous online groups, it's never a good idea to bash the work of other writers, whether they are published or not, whether YOU are published or not. The writing community should boost its members and offer constructive advice on improving the craft. No one appreciates a "know-it-all" who sets him or herself up as an expert on the craft of writing (especially if their own writing doesn't reflect it.)
Secondly, be open to constructive advice (or criticism) about your own work. To be so enamored of your own work that you can't possibly see any room for improvement is a sure-fire way to set yourself up for failure. No one is perfect. Everyone can improve. And yes, criticism or a negative review of your work can hurt. Becoming defensive and lashing out at the reviewer or critique partner and questioning their reasons without taking a good hard look at WHY they had a problem with your work is not going to help you in the long run. Here, the key is to start with people you know personally who can be honest with you and have your best interests at heart. If they tell you that your work needs *ahem* work, then do yourself a favor and listen to them before you unleash your work on the less understanding, more critical public. Many people don't feel the need to be nice in a public forum, especially online.
Third, when you're attending a book event where an author is discussing their work and trying to sell their work, do not be the writer who takes advantage of a captive audience to promote your own book. That author may have traveled a long distance to get to the venue and only has a set amount of time. That author is there to talk about HIS or HER own book, not anyone else's... especially yours. And trying to steal their limelight means they won't have anything nice to say about you to anyone else (especially their publisher!)
In conjunction with that, it's also bad form to approach the author after the event and tout your book in hopes of gaining some promotional boost from a "big league" author. Some authors might not mind, but many barely have the time to write and promote their own books. And not everyone is willing or has the time to mentor an aspiring author. They worked hard to get to where they are; you shouldn't expect anyone to make it any easier for you. And don't ask them to "put in a good word for you" with their publisher. They are not going to jeopardize their career to push an author they 1) do not know, and 2) whose work they have not read.
Lastly, and this is hard for a lot of fledgling writers to accept, there ARE other things to talk about besides writing (and by "writing", I mean your own writing.) If someone asks what you do for a living or what you like to do, by all means, take the opportunity to speak of your work (especially if you're published and trying to sell it!) but DON'T kill all future conversation and possible friendship by talking exclusively about yourself and your work. You'll make a far more lasting and favorable impression on people if you talk about other things and show you're a well-rounded person, not someone who obsesses about themselves and their writing. And if someone mentions that they, too, are a writer, offer them encouragement and wish them well.
Always remember where you came from, think about where you're going, and consider who you would like to have with you when you get there. It can be lonely at the top... and at the bottom, if you're not careful about how you climb that ladder.