Every putt is therefore effectively a straight putt, it all depends on how hard you hit it as to whether it takes any break.
With your pace of putt in mind, pick the break you envisage the putt will take. Then pick your target out as a straight line and hit the ball at the right speed so that it takes the break.
When you approach the green it is important therefore to look at the contours and assess the slopes and lie of the land.
Firstly assess whether the put is uphill, downhill or across any slope.