Then the price of the product must be kept in mind, the price is the most important (their own price, the market price). Now a lot of big companies, schools, businesses manage the procurement side are likely to have a rebate (everyone knows, you must of course know)
Lastly you have to run more places, more business cards, after-sales service to keep up.
Other details will not be explained.
I do office supplies has been 5 years, the above are my summarized experience, I hope you useful!