I use trend lines in my trading, generally on the daily charts to mark support and resistance. I want to know where the stops are, especially a cluster of higher highs or lower lows, these can be great opportunities....
However, we tend to give too much weight to lines on a chart. To prove that these lines are pretty much useless and that we give them too much weight, try this exercise for a week.
Step 1:
Pick you favorite intra-day market and draw some random horizontal lines across and through the most recent range, save the chart or whatever you need to do to keep the lines.
Step 2:
After the next session, check the chart and see how the market "reacted" to the lines. Rinse and repeat.
Have fun.
CanOz