Always be the first one to give a number. That sets the bar. Let's say your current salary is $100K. You want $130K. You say call the number first, $160K. Now the company is negotiating against that number. If you accept $140K they will perceive it as a win for them.
The problem is most engineers significantly under value their worth and so usually offer a low-to-the-company number. There are people working in offices (not as programmers) that don't know zip files. You, as a programmer, can do magic with the magic boxes.
In the long run, it would be better if programmers were better are valuing themselves. In the short run if programmers stopped giving numbers, it'd be better.
