In the series of three fairly high dose (7+g) of Syrian Rue brews I recently did, with the middle one I failed to take into account that I had eaten dried meat (nitrite free) in the form of chorizo-like, pork and beef "Jägerwurst" sausages at lunchtime and the difference was quite marked compared to the other two sessions where I had stayed vegetarian. There was quite a mælstrøm of negative thoughts, which seemed clearly attributable to this dietary factor both at the time and still now. There was certainly some serious business going on, which I don't entirely mind, but that would have been a bit much to handle for a neophyte.
This suggests to me it would be best to stick to a vegetarian diet while doing this kind of stuff. The other two sessions were smooth as anything, much more euphoric.
Regarding fluids, I drank a lot of herb tea around the first session and it was quite amusing the amount of highly fluorescent harmala piss I was producing. This made the first session rather milder.