I hate that question. You feel always feel if you put too high you won't get a call back and if you put to low you feel you got suckered once you find out how much everyone else makes. I prefer to call the hiring manager and ask what the salary range is that they are willing to pay and then put something in that range if I still want it for that range. If I can't find out the range I put 10% over what I ideally want for the job. Of course I've also applied for things I wasn't interested in and told them what I thought was an insane salary range and still gotten call backs so its hard to say.