Turn them on. Let the electricity heat them up for an hour, then gently tug on each strand if necessary to get them to hang lower. Usually, the heat from the electricity alone will give you the desired effect over time.
For the last two years that I did so, I hung ours and just unsnarled them, but left them all bunched up. I actually heard more positive then when I went through the grief of straightening them. Who would think?