Using leader lines effectively
Leader lines should only be used when necessary. Remember that you don't want anything on your slides that is unnecessary. Don't use leader lines as a design element; they're a tool.
When you do need to use leader lines, the following are good guidelines for formatting and editing so your slide will look clean and consistent. The graphic below shows examples of two different types of charts that frequently need leader lines: data-driven segmented column chart and a diagonal arrow on two axes. Draw and size 1 leader line that is appropriate for your use (see below that the leader lines are drawn differently depending on how they are used). Make copies and align as appropriate.
Now you're ready to make your adjustments, and here is where consistency comes into play.
By editing the leader lines in this manner, you have kept a consistent look for the leader lines and for your slide.