First, try to find someplace that is quiet and free from distractions and interruptions. This makes it easier to relax, and concentrate on the reading.
Second, I think it is absolutely essential that you ground and center. This helps to protect you, and ensures that the energy that you use in a reading comes from the earth and the universe, and not from your own body, or that of the person you are reading for. That will keep you from feeling drained and depleted following a reading, and will also make the reading more accurate. I can't stress the importance of this enough.
Third, figure out the question you want to ask. This is often the hardest part. I think there are basically three kinds of questions. A "What do I need to know about this?" question is the simplest and most straightforward, and can be asked just like that.
"Should I do A or B?" questions need to be phrased carefully. In fact, if that is your problem, I recommend asking first, "What will happen if I do A?" and then doing another reading for, "What will happen if I do B?" Then choose the outcome you like the best.
The most commonly asked questions, of course, are yes/no questions, "Does he love me?" or "Will I get money?" These need to be phrased carefully, or the answers can be very confusing. You may want to try a 3 card yes/no spread for simple questions. But for more complex ones, try phrasing them like, "What is going on with our relationship?" or "What is ahead financially?" You get the idea. Phrase the question to elicit the greatest amount of useful information you can.
Pretend you have to answer the question, with only 78 different pictures to communicate the answer, and phrase it so that it's possible to do! After all, that's exactly what you are doing here.
Fourth, mentally state your purpose and intent, and dedicate the reading to the God or Gods of your choice to ensure that the truth will come out for the good of all, and by the free will of all. The wording is up to you. And if you are an atheist or agnostic, dedicate it to Truth itself. The point of the exercise is to let your subconscious know that you aren't playing games here, and you really want to know the truth.
Then shuffle, while concentrating on the question, until the cards feel "right." Cut the cards, and begin to lay them out in the spread of your choice!