You shouldn't just wake up and decide to do it. If you have worked with a demon for some time and have put a lot of thought into it then you should choose. If you think it's cool or something, don't.
I've never done it, nor have I wanted to, but I would study a specific demon to know as much as you can, then invite them into your home and try to build a partnership with them, after all that, then try. You can summon a demon for help, but if you don't know what you're doing they will take advantage of you.