Use condensed text and double-sided printing wherever possible to use fewer pages. The post office will work with you on this. Use electronic communications where possible. Stock fax machines and copiers with paper that has been used on one side. This prevents paper from sticking due to changes in humidity.
Some suppliers take paper curl into account and indicate which side of the paper to print on first.
When manually duplexing, let the paper cool a bit before running it through again. Keep your machines cleaned and maintained according to manufacturer specifications to reduce problems associated with paper dust, which is produced by both recycled and virgin papers.