Pre-qualify the landscapers you invite to bid on your work. Ask your friends and neighbors about their experiences with landscapers and prepare a list of question to ask before you invite any landscapers to your home. While not all customers want to have their names and telephone numbers given out in a general listing, addresses of completed and on-going jobs should be available. The license will assure you that the company is operating legally, and that the owner has passed examinations demonstrating experience, knowledge, and a level of professionalism.
Automated information is available at all times, giving current status and complaint information.
A license number on a business card is not always valid or current, or it may not even belong to that company. Ask for proof of insurance coverage and check the company's limits and policy expiration date. If the company has employees, check to be sure they carry worker's compensation insurance. A quality design and estimate takes time - yours and the landscaper's. The more knowledgable you are, and the more information you have from each landscaper, the easier it is to compare one quote to another.