Make an effort to catch people doing something right and then be sure you let that person know what he or she did well and how it matters to the you and the company. Separate the positive feedback from negative, so people really hear your acknowledgements and embody the success.
One example of positive feedback that has made a huge difference in our small business is saying thank you to the person who processed the payment for an invoice.
We typically work within corporate environments where the person who hires us, works with us and pays us are all different people. By thanking the person we are communicating with, we humanize the whole process and gain an ally for future work.