How do you determine the trigger price to the penny (or dime)?

Dear Pat, I am trying to duplicate your process on how you determine your trigger price that you determine for your stocks. The key list stocks. I am trying to grasp what previous high to look at and why? I see that they are different from MarketSmith or IBD or any other source that would have a buy point set for a stock.  As always, thank you very much! Eric