some people have a tendency to elevete their shoulders at the very beginning of the dance as they take their partner...try this:
stand with feet closed, arms at sides and in a relaxed position. raise both arms straight out from your side (like an "airplane") you should notice that bringing your arms up laterally like this causes the shoulders to AUTOMATICALLY raise and tense
now, stand in the same relaxed position, hands at sides. raise both arms to 90 degrees in FRONT of you (like old B-rate movie mummies) then seperate arms to each side. Notice that this action allows the shoulders to remain down and realxed. You see this movement in ballet as well.
so, don't sabotage yourself from the very beginning. practicing taking your partner by raising your arms fwd. and then out will both get you in good starting posture and will help you to understand the proper "feel" of the shoulders so that you can more easily accomplsh it while dancing
Good luck, M