I generally don't actually believe in superstitions, but I am still a participant. Part of it's just engraved in who I am, I guess.
I do knock on wood.
I don't wash clothes on New Year's Day (or else you'll wash someone out of your life in the next year), and my family prepares all of the "good luck" foods for New Year's - black eyed peas, greens of some sort, etc. The first person walking in through the door is supposed to be a (preferably dark haired) handsome male.
I also try to make it a point to get wet in the first May rain (good health for the rest of the year).
If I find an inch worm on my clothing, I leave him (unless he would otherwise be in danger), because to find one on you means he's measuring you for a new coat.
I love black cats and think they're beautiful, so I call them good omens.
Am I willing participant? Absolutely. I think they're fun.
Do I really believe them? Eh, it's hard to say. Some more than others. I don't REALLY think an inch worm means I'll get a new coat, but it's nice to say it. And for getting wet in the May rain - bet your bottom dollar, if it comes at three in the morning, my behind is staying cozy in bed where I'll be warm.
That being said, I think I'm pretty accepting of other people's superstitions, even when I don't understand them. I won't always honor something if it's a request that will make my routine or life much more difficult, but for the most part, they don't. I won't throw salt over my shoulder, for example, if I'm in a restaurant with another table seated behind me. I might do it if there was no one behind me. My family has never practiced the whole thing about spilling then throwing salt, so someone would have to pointedly ask me to do it.