I had this spread passed on to me, and it really is effective, I've done it for myself, and a number of other people, all of whom have been surprised at the accuracy.
You need the whole deck, seperated into Major Arcana, each seperate suit, and the Court Cards.
Arrange each stack in a circle, with the Major Arcana at about 8o'clock on a clock face. The sequence goes:
1) Major Arcana
2) Wands
3) Cups
4) Swords
5) Pentacles
6) Court Cards
Next you turn over the top card, after having shuffled well obviously). The top card is your best or strongest aspect of your personality, what you can use best to achieve any dreams you have:
1) Your greatest Spiritual Strength
2) Your most enterprising characteristic
3) Your best emotional strength
4) Your strongest response to problems
5) Your most admirable financial/resource ability
6) Your favourite aspect of your personality
Once you've looked at those cards, and understood them, you take the bottom card of each pile and lay it horizontally across the top card. These cards are where you are least happy with your personality, and once you understand them, you'll be able to do something about them, and hence improve yourself and your life:
1) Your most important Spiritual challenge at this time
2) Your most problematic attitude towards work
3) Your most difficult emotional challenge at this time
4) Your worst fear when facing problems
5) Your financial weakness
6) Your least favourite aspect of your personality
Finally, once you have understood the second set of cards, you can tie them together to see how you can get them to work together to help you with life.
On an added note, though this wasn't suggested when I was told about this spread, what could work is having a second tarot deck next to you as well, so that if there are cards that you simply cannot work out, you can pull clarifying cards, which will be mixed, and get additional help from them.
I hope that helps you.
