I only attend cons that invite me.
I get invited to a lot of cons, and cons are very expensive for most writers to attend, since most of us can’t sell art or do commissions to help with expenses.
So I can really only go to the ones I am invited to, but fortunately, I am invited to many, many times more cons each year than I can possibly attend. I’ve turned down well over fifty this year alone so far, for real.
If you are a guest of a con, at their invitation, you are given a table if you want one. I often don’t need one at cons like SDCC and NYCC, but at smaller cons, it’s nice to have a set place to do signings and meet readers.