If you have watched videos of trail courses or looked at any photos you will have noticed the wide array that poles can be positioned.
Some of the most challenging are the lope overs because of the precise movement required in order to maneuver over the rails without ticking them.
This excellent article goes over training your horse and yourself how to master the lope over.
http://www.equisearch.com/horses_riding_training/western/pattern_events/stridelength_112206/
We've been practicing this the last couple of weeks and have seen a great improvement. Both the horse and the rider have learned how to space themselves appropriately. And a small hint - it is a lot easier and faster to master when using striped poles.
The stripes on a poll are typically in 2 foot increments, except for the very ends which are white and only one foot. Make sure you read the article to get the full idea.
Have fun out there!