THere can be a temperature change. It's been over 9 years since I charted so I can't tell you the details at this point. sorry. that book will outline it well though. You would take your temp every morning at exactly the same time(ish) before you got out of bed. You'll see there's a pattern develop where your temp goes up slightly - not a temperture, per se, but if your norm is 98.6, you may see it peek out at 99.0. The next day it drops suddenly - a cue that you've ovulated already. Window closed.
A rough estimate is you ovulate in EXACTLY the middle of your normal cycle. IF you're on a 28 day cycle you ovulate on day 14.However, that implies you have a text book cycle and not everyone does. Some can be off a few days in either direction. Some can have erratic cycles, etc. Figure yours out and use the mid-point as a guesstimate. Have sex the 3 days prior to that date and a couple of days after to be sure.
at 6:08 AM on Jun. 25, 2011