Here's something that worked well for me: I deferred the salary question until after I'd had some contact with my potential employer (rather than the recruiter) so they had a sense of my value. Then, when asked what my current salary was, I said something along the lines of the following: "my current salary is well below where I want it to be, because I started out in a low-level job and worked my way up getting the…
It has nothing to do with "screwing people". This is terrible advice. Salary negotiation is the single most important financial decision you will make in your life. That shit compounds , son! Do. Not. Give. Them. A. Figure. First. Don't! @patio11 explains why in exquisite detail here: http://www.kalzumeus.com/2012/01/23/salary-negotiation/
What I've suggested, contrary to your (unnecessarily abrasive) reply, is not to give up on negotiations but to push past the impersonal arguing over numbers and get to the actual negotiation at hand by laying not only your own cards, but the other person's cards, on the table. You implicitly say up front "if you try to pull the same old $salary * 1.1 game with me I'll turn down your offer" while also laying out what your expectation is. You name a number, and say "that number is not good enough, make it better" and thus leave the ball in their court. This is not you saying "well I want a better salary than I have now, I make £20,000 and I will accept £27,000" - you're saying "well I want a better salary than I have now, I know I'm underpaid, I make £20,000 right now - it's on you to guess what I place my value at, but you know it's not a small jump".
All this without making you look like a distrustful asshole like many of the previous suggestions would do.
Oh, and I forgot to mention in my previous comment - you can be ambiguous about the amount you make too if you want, e.g. "I make below market rate" or "I make about 2/3 of what my friend makes for the same job". But it's very transparent.