If you're going to start with salary, at least don't tell them what you currently make, because that will instantly be their baseline. Just tell them what you desire and don't tell them that it is 20% or whatever more than what you currently make.

But really you shouldn't start with giving a number. They already have a huge advantage because they negotiate salary all day and you do it once every few years. Just ask them for the range and make sure the minimum is above your X+20% number. If it's not, let them know that their range is too low, and if they won't tell you, say, "thank you, next".