Be sure that you are able to present clear benefits that a reseller would have by selling your product. Detail the compensation, the product, and your level of support to them as a reseller. Also important is who handles customer support. At this level, the business case for your product is just as important as the actual product itself. Having a case study or two at hand to send them if they are interested would be extremely beneficial.
Prepare your answers to any questions they may have. You should be able to answer any question about the product, its market, and its sales history.
Find the proper contact for each reseller on your list. If possible, find people who can make decisions.
Tailor your pitch to each company. Research the company first and try to understand their market and how your product will benefit their customers.
Keep the call or email short and professional. Be assertive, but not too pushy. Don't leave the onus of contact on them. Tell them you will contact them again if they are even marginally interested.
If you say you're going to call back or email, do it and do it on time.