Many years ago, I found this formula from Forbes.com to predict the next day's support and resistance of a stock price using previous day (High, Low, Close). By the way, I never watched it closely, nor confirmed its credibility. It's good if somebody have a watch on it and give some feedback about its validity. Here we are...
H = previous day's high
L = previous day's low
C = previous day's close
Pivot Point (P) = (H + L + C) / 3
First area of resistance : R1 = 2P - L
First area of support : S1 = 2P - H
Second area of resistance: R2 = P + H - L
Second area of support : S2 = P - H + L
Example of Nortel Networks Corporation. (NYSE: NT)
Date Open High Low Close
13-Aug-08 5.91 6.01 5.80 5.93
P = (6.01 + 5.80 + 5.93) / 3 = 5.91333
R1 = 2 * 5.91333 - 5.80 = 6.03
S1 = 2 * 5.91333 - 6.01 = 5.82
R2 = 5.91333 + 6.01 - 5.80 = 6.12
S2 = 5.91333 - 6.01 + 5.80 = 5.70
Hence, today's resistance & support will be ($6.03, $5.82) or ($6.12, $5.70).
PS: This formula is applicable if and only if there is no major news about NT, meaning that it's trading within a normal breath.