As I mentioned in the lesson 10, I tend to give my clients a 3-4 minute summary of my own Tarot philosophy.
I also ask them not to tell me anything, as I don't want to be influenced when I do their first spread.
If you take this approach you can use the Celtic Cross, a great general spread, to get a feeling for their current circumstances, concerns and focus. I then perform 2-3 additional spreads to further develop the picture of events, before I ask if they would like to ask the cards any specific questions.
For specific questions, I tend to use the 3 card spread - influences from the past, advice, outcome - to help find a solution to their problem or an answer.
My readings generally last about one hour, although I can do one-spread readings or shorter readings of half an hour, however, my clients seem to get more value from spending the full hour with me for a face to face reading.
Obviously, you need to decide what duration of time you feel comfortable with - some people prefer to deliver their readings very quickly - say within 20 minutes - whilst others are happy to spend several hours with a client. Everyone is different.
Again, give yourself enough practice with your friends and you will soon develop your own 'way' or 'style'.