Always check out the background of a writing conference long before going. They’ll either be well established with lots of credentials (Winchester is a good example) or admit they’re new but have a credible “guest” list of speakers, most of whom you will have heard of!
Other advantages of a good writing conference that I've discovered to be true are:-
Going to a suitable conference helps make you feel like a proper writer. This can work wonders for your self confidence. It’s very easy when working on your own to not feel like a writer, to ask yourself who are you kidding when the doubts set in, so making yourself go to one of these conferences can be a way of helping you overcome your doubts.
You learn a lot from the lectures!
You meet other writers and it is wonderful comparing notes and giving each other encouragement.
You can learn about the industry, vital if you want to join it.
Some conferences have writing competitions. Winning one or being shortlisted is a great thing to add to your writing CV.