Some people use a crystal ball, tea leaves, planetary alignments, Chinese sticks, tarot cards, numerology or palm reading.
I am a scientist so I use more statistically-based method.
I use a formula to derive a single measure that takes into account the leading economic indicators from the past 17months and I plot that value on a graph against both the S&P500, Lehman Brothers Aggregate Bond index, petroleum futures and gold prices.
Where all lines intersect (or closest to intersection) I draw a one inch red circle.
Then I post that graph 100yrds away, load up a 30round mag, aim my Bushmaster at the dot and fire away. If all of the brass that's ejected falls within a three foot circle, then I know the recession is over. [:P]