Last week, I dropped my tips for meditation and how it has changed my life - allowing me to burn off stress and train my body and mind to handle even more stress. More specifically, we discussed Christianity and Meditation. Make sure you check out that episode if you have any religious hangups about meditation.
Basically it is a forced disconnect from distraction. It forces you into a state of meditation.
I use it for stress relief and when I'm done, I feel as if I had a nights' sleep...seriously.
So, a float tank is a closed tank where there is no light and no sound and because you're floating in salt water, you aren't touching any of the walls. You're like floating in space with just you and your thoughts. And ideally, not even them, because you're meditating.
I love pitch black tanks, but I have had tank experiences with lights, some that are open and not closed at all. I have had some that played music the whole time and some that only play when you're done. They all work, but you will start to have a preference.
There's your tutorial. My advice is to start easy and work into it. Start with a large tank and have the light be optional. Try and use that time to meditate but don't force yourself if you can't. Just enjoy the quiet.