Try to narrow down your choices to three providers. Then ask each contender for samples similar to your project (note that ink quality can vary across providers), as well as names and numbers of customers that have used the house at least twice.

Most importantly, request a quote. To help your negotiating, request written bids that outline each specific aspect of your job and the cost of each service - not just one that provides a per-piece and total cost.

Be prepared to go back and forth with the vendor, answering questions about what exactly you want. These jobs need to be precise, and if the vendors have questions, it just means they're taking your job seriously.