Oh there are SO many things you can use! For my first time out, I used strips of soft cloth I cut, looped it around a stem and pinned it to my fabric pot when I had pulled the stem as far as I wanted... if you're not using fabric pots, you'd have to punch holes in your pot and thread the strips through them to tie them off... others use plastic coated plant wire, string, what-have-you... Now I'm using LST clips I bought from my local grow store that bend the stem at a 90-degree angle... I really like using them and they're reusable which is a big plus for me! You can use pretty much anything that will hold a stem in the position you want without harming the stem.
Good luck! It's easier than you may think!