Good questions and points you bring up Xt. Here's how it works for me. My ceremony begins by cleaning up my space and then I go and spend at least part of the day walking in nature. It helps to have a large wilderness area within steps of your back door! I visit some of my favorite spots, make tobacco offerings to various plants and say a prayer of gratitude.
I come home, smudge my journey space and perform a small pipe ceremony, giving blessings to the seven parts of the medecine wheel. If I feel the need or want to send some healing thoughts I will pray to Christ. I'm not even a christian, at least not in the traditional sense, I just do what seems to work for me. I then do some yoga stretches until it's time to drink.
I mostly draw from native american spiritual influences because it's what seems the most straightforward and familiar to me and there is a framework ( There's that word, You said it first Tripper

) already in place for honoring Mother Earth. If you have used ayahuasca you know that she wants you to connect with the earth spirits. So do mushrooms and cactus but Mama's really in your face about it.
I'm not fanatical about any of this but if you have no belief that there is a spirit realm on the other side of the mirror then these types of ceremonies are probably a a big waste of effort for you. That said, I don't believe you have to have any kind of traditional belief system in order to use these plants. For instance, I find the people of the Amazon really fascinating, but their way doesn't fit into my framework well. It's all just too culturally foreign to me so I would feel awkward and dishonest about trying to walk that path.
But still, I can borrow parts that are relevant to my worldview. It's what humans have done for thousands of years. We use what is relevant to our cultural perspective and discard what's not. I suppose the reason the native (north) american system works for me is because I'm living on the same ground they occupied for thousands of years. Some of that is going to have to rub off if you're open to it. It is also adaptable to a modern perspective in a lot of ways, and I can still find room for teachings from many other sources.
In the end it's about directing our intent to best suit our purposes. If your intentions are from the heart, it can do nothing but help, and practicing a ceremony, even if it's your own little creation will help cement those intentions in place. Hopefully resulting in a journey with greater personal insight and meaning.
Thanks drishti, interesting thread, glad to see it finally getting some interest
Peace.
As Within, So Without.