This is primarily regarding DMT, though I have essentially followed the same ritual before partaking in Salvia Divinorum, as well.

Usually I start feeling "the call" a few days, or sometimes even weeks, beforehand. For the days leading up to the journey, I reduce the amount of external stimulation and try to focus inward. I will try to avoid technology as much as possible, don't listen to music, try to spend as much time outdoors, away from people & noise, etc. As The Hermit said, I also try to increase the frequency of meditation I am performing, though, ideally, I should be doing this already.

Usually, I know I'm going to journey as soon as I wake up in the morning on that day. There's a very solemn, ominous sense of "facing the music," so to speak - I can't put it off anymore. Nothing else will help me get over this hurdle. This is the only way. I try not to eat for a few hours beforehand. I smudge with white sage, & light incense - I use one scent exclusively for journeys, because I feel that the familiarity & association will give me some sort of anchor or reference point, when things inevitably get rough. Some stretches beforehand, especially headstands, really get the blood flowing and give you the sense of "being in your own body," shortly before forcefully ejecting your consciousness out of this realm.

I wear a set of Rosary beads around my wrist that belonged to my grandmother. They were given to me by my father after she died. I always kept them with me. Originally, it was a "good luck charm" for journeying. After several more journeys, I sarcastically referred to her as my "guardian spirit" in that dimension. Several more journeys later, the sarcasm disappeared. Interacting with the deceased in these states of mind might be some sort of a controversial topic to discuss, but I have had experiences that have legitimately shaken me to the core of my being and left me staring at a wall with my jaw hanging open for a solid twenty minutes wondering what the hell any of this means.

Once I'm ready, I sit cross legged on my bed, cover myself with blankets if it's cold, and hold my GVG and torch lighter. I stare at them hard. I lift the bowl up to my nose & breathe in that smell - how do you even describe that smell? It's enough to make my heart start racing & I began performing breathing exercises to calm myself. I recite the Litany Against Fear (yes, I'm a Dune nerd), & my grip gets tighter and tighter around the pipe & the lighter as I speak each line with more and more conviction. I kiss the cross on my wrist, say "Protect me, Nonna," then I hold the pipe up to my mouth, light it, & you know what happens next.