I don't have too many habbits, just a few observances I like to follow for various reasons.
I do wash my hands beforehand. In fact I do everything necessary to make sure I won't need to get up for about two hours, because that's becoming the average time I spend on a reading. I take care of, uh, nature, and be sure to have a drink nearby, etc. I don't like to get up in the middle of a reading because I think it just breaks up the concentration and the flow of the reading.
Then I make sure there is silence, or if I'm in an environment where I can't control the noise around me (such as if someone's watching TV and I don't want to go into another room), I will put my earphones in, which block out almost all noise. I don't like to have any noise, because I feel it can have an effect on the mood of the reading, or at least distract me.
Then I hold the cards, and say the prayer mentioned at the beginning of the Opening of the Key spread.
I invoke thee, I A O, that thou wilt send H R U, the great Angel that is set over the operations of this Secret Wisdom, to lay his hand invisibly upon these consecrated cards of art, that thereby we may obtain true knowledge of hidden things, to the glory of thine ineffable Name. Amen.
I didn't think when I first began that this would really affect anything, but I fine my readings are much better when it is included. I mean much better almost to an unbelievable extent in their accuracy.
And then I start. Given that all my readings are done over the internet, and that I use braille cards and it's hard for me to keep them all organized when they are spread out, I don't actually spread the cards out. I simply type the name of each card in a list, starting at the bottom of the pile. It also helps me to do pairing and counting a lot faster, and to look up certain details if I need to, such as if a certain major card is zodiacal or planetary, or the date associated with a certain card, etc, since I have not yet memorized all of this. I use a laptop so I can pretty much be wherever I need to be and am not confined to one space.
Afterwards, I respectfully put the cards back in their container, sometimes giving some sort of thanks.