Trend lines are drawn on charts to help predict the general direction of price.It also help to determine good entry and exit point.they also help to see the reversals.
I find that when the price make higher high or lower low then we can draw trend line . Trend lines is an important part of technical analysis . If a trader can draw trend lines as a perfectly then he can make huge profit in a short time . But trader need more and more practice fort hat . Trader should not draw trend line forcefully !!