Christmas Decor on the Ceiling?

I have a lot of gorgeous white willow branches that I wanted to use for Christmas decorating. The idea is to hang the branches from the ceiling, with lights attached and ornaments hanging from the branches. I'm trying to figure out if I should put the lights on the ceiling before I put the branches up or after I put the branches up. Or should I put the lights on the branches themselves? The other thing is-and this is the biggest problem- I have a cement ceiling and I cannot figure out how to attach something as heavy as branches to hang from the ceiling. I thought about maybe holding the branches up by nailing cord in a grid pattern from one side of the wall to the other as I add branches to the ceiling, one area at a time, then maybe running small white lights along the cords, then hanging ornaments from the branches. One thing I cannot do is screw holes into the ceiling. Am I missing something? Is there something I haven't thought of? I really need some advice, ideas, etc. Thank you for your time and creativity, I will pick an answer.