I've been working in the IT industry for the past 20 years and have done everything from coding to QA and system test. I have a BS in Computer Science and currently work as a tester in a Test/QA organization. I've been offered a position as the Team Lead (the current Lead is being promoted to another position) for the group (that supports 3 different projects) that I work in. I don't have specific management experience but for the test project that I work on, I've been the group leader for the past year. As Team Lead, I'd be responsible for the entire team (3 projects) and have 20 direct reports. The Team Lead position would mean a lot more responsibility. Should I ask for a raise and if so when?
It really depends on whether you want to become a team lead and deal with 20 team members and several direct and indirect bosses more than your employer wants you specifically to be the team lead. The commodity that is more in demand always commands a higher price. If your desire to become a team lead is more than your employer's desire to have you as the team lead, then the commodity you desire has a higher price and so you have to prove yourself first as a team lead for about 6 months before you ask for a raise.
If you are not interested in the team lead position unless there is a raise, then it is better to ask about a raise before you take up the team lead position or as soon as possible if you have already taken up that position, so you can decline it right away.
You should ask for a raise to at least put it on the radar that you know that the position is worth more than what you are currently making. Your company would likely be happy to continue paying you what you are presently making so you are the only one to gain by bringing it up.
As to when, definitley before you take on the role. The urgency of the situation is entirely based on when you will take on the extra responsibilities. If you start tomorrow book a meeting with HR and your manager today.
You should ask for a rise before taking the new role you need to compare your current salary to what the other team leads are getting and ask for say 10% more