Always ask for proof of license. Ask if their estimates can be itemized for possible litigation purposes. The internet is also a great source for information. The NAHB has a registry of contractors who have successfully received training concerning EIFS directly from them. D. Look at and talk to the contractors.
First impressions can be very telling.
Remember, the owner or superintendent is probably the neatest one of the bunch. It has become common practice for contractors to request a fee for some estimates. A professional contractor will credit the estimate fee back to the customer if work is approved and completed per the contract. If you are still comfortable with them after a chat, invite them to bid on the job. Provide each with the same scope of work.