Profit taking with percentages

Hey Pat, when deciding on sells do you ever use percentages as a sell signal? For example, the stock is now up 7-8% from your buy point so you sell 1/4th. Then the stock continues up and hits 15% from your buy point and you sell another 1/4th, etc. 

Or are you making your sells strictly based of price action and volume and however good or bad that is determines when you sell some off?   Hope this all makes sense! Thanks