Yes, you wait for them to provide you with an offer before you start negotiating. If they ask during the interview about your salary expectations, you can say, "I am just focused on the position and organization right now and want to ensure that I am are right fit for the job." If they insist, you can ask them what their budget or budget range is. If they really insist, be ready with a range that you have researched in advance. The general rule is that the first party to mention money sets the limits. If you mention a number before they do and it is lower than what they had budgeted, you just did them a huge favor by saving them money.