I would have to agree that being outdoors lounged out on a blue sky sun filled day is a prime setting, especially if you aren't around neighbors or people and have some level of privacy. It's very special ime. The openness of the outdoors, mixed with all the other factors can really allow an 'easing up' of the experience, even when it goes full-bore and rips you and your reality apart.

The other option for me is indoors in a low-lit room, or a room with just a couple candles near by. The interplay of dancing shadows and natural light can really coax the experience out and induce this deep sense of comfort. I also occasionally like a completely darkened room in order to get a full uninterrupted display from the Other Side. Also, the low lighting or no light indoors can really help ease things if there's a rampant comeup, as fluorescent lighting and whatnot can [ime] induce occasional panic, which no lighting/low lighting can completely preclude.