I've heard some people say that you should push your accessory exercises as hard as you can and use as much weight as you can for whatever rep scheme you're using. I've also heard that you shouldn't push too hard on accessory exercises because they're just used to help along the main exercises. Which way would be best? Are there any rules for accessory exercises?
The only differences I see are that there are a number of accessory exercises that are better suited to high rep work, or only to medium and high, while most main exercises are suited to low rep work as well.
Sometimes this is for safety reasons and sometimes simply because it works better that way.
For example, generally speaking one doesn't strap on a dip belt and a heavy DB to go do triples on the triceps pressdown.