It seems obvious advice but it really does pay (!) to do your homework when it comes to salaries. I have come across some people who know so much – what competitors pay, what options to ask for, what their future colleagues are likely to be on, there is a lot of knowledge that could help in the negotiation. Check on glassdoor, linkedin (which seems to show salary ranges now), and ask around. Once you’re in the company, it becomes hard to change anything and so always try to get the best deal from the start.