I love conventions. I've been going to them for over ten years. I started at small anime conventions and graduated to DragonCon and GenCon in recent years. When many writers approach me for advice on what they can do to improve their craft, I usually tell them to find a convention with a good literary track and to go to the panels and take notes.
Many fantasy and science-fiction conventions have tracks devoted to writing and publishing. You can learn a lot from listening to professionals talk about their craft AND better yet, it can be a great chance to meet other writers and network. Many of the writers that come to conventions are happy to talk shop with you and answer any questions you have.
Now, there are also a lot of writing conferences, and I've been to quite a few of those and they are also a great resource for writers at many levels in their careers. I've found the main differences between a convention and a conference is: