Small businesses are the cornerstone of the U.S. economy, representing 99.7 percent of all U.S. employers, according to the U.S. Small Business Administration's Office of Advocacy.

A vast amount of small package freight moves throughout the United States on behalf of these companies, and in most cases, parcel carriers such as FedEx, UPS, and the U.S. Postal Service are employed to ship and receive the goods.

Given DHL's entry into the domestic small package arena this year, and recent rate hikes from FedEx and UPS, now is a good time for companies to revisit their small package contracts.

Many companies make the mistake of dusting off contracts only at the one- or two-year renewal mark. Companies should instead review contracts early and often to ensure they receive the most competitive, market-driven shipping rates.

When a contract no longer aligns with a company's business, re-negotiation is a must. Here are some tips companies can use to master small package service contract negotiations.