Understand your own real needs -- Before you choose any waterproofing supplier, try to understand what it is that your business needs, goals and what you are hoping to achieve with this vendor relationship.  Make sure to tell your waterproofing supplier about those needs, goals and hopes, so that everyone knows your expectations in advance and both of you are moving in the same direction to the same destination.

Your values and objectives line-up with your waterproofing supplier's. -- At Grate Products we have 4 Core Values, and we make sure that the contractors that we work with are also committed to those same values and ethics.  It's much easier to find common ground with other companies when you all understand the foundational values that make your company work.

Your primary business requirements are the focus of the waterproofing supplier, and not a side business -- We've all seen too many times over the crazy selections of the big box stores.  They carry everything under the sun, and that makes them into a Jack of All Trades, Master of None.  You shop for pet food in a pet food store, but you can still buy it at a grocery store.  One store is focused on you and your pet with experts on hand, the other is just looking to fill a shelf.  Talk to your waterproofing supplier and determine their actual focus, and make sure that they align with your actual requirements. 

Building and sustaining the relationships -- Ask for references from the waterproofing supplier.  You'd like to talk to a couple of the companies that they service in your industry to see how they are really doing on the ground.  You'll quickly find the difference between an order taker and a real partner.  If you only talk to your waterproofing supplier when they call you to make an order, making you feel like a Drive-Thru customer, then really consider if that's a good thing or not.  Talk to people that have had real issues resolvesd by real field experience with those products.  Talk to people that have asked outrageous (and really cool) questions about complex and complicated projects, and then worked out the solutions, with real product experts.

Talk to your staff about that waterproofing supplier. -- Has anyone heard anything good?  Bad?  Other issues?  Do you already buy some things from that vendor, but not others?  Have you, or your staff, had positive, negative or neutral interactions with the supplier?  Discuss these things and make sure that everyone involved knows what you're looking to accomplish with the waterproofing vendor, and then ask for input and buy-off.  Everyone moving in the same direction, to the same goals, is always easier.