Factors to consider:

1. References - contact neighbors to see who they have used.

Determine if your project is similar in size and scope
Determine what type of reputation the contractor has earned for:
Dependability
Capacity
Ability
Timeliness of response

Ask the contractor for a list of professional associations to which they belong. The MNLA or one of the chapters.

Ask whether the contractor has been professionally certified in any way. Has the contractor earned certification from reputable programs such as?

Determine whether the contractor employs people qualified in each area of expertise.
Determine if the contractor employs sufficient numbers of field and office staff
Determine if the contractor has the right equipment to handle the type of work you're asking to be done.

Does the contractor have an office, voice mail or answering service?
Determine how long it takes for the contractor to return calls.

A written and signed contract will protect both the homeowner and the contractor. The contract should clearly spell out the scope of the project, a start date, when the project should be finished. It should also include all payment schedules. A good contract will also define procedures for the approval of change orders and costs of extras.

Your choice of a contractor should be based primarily on the creativity of the design presented, the salesmanship demonstrated by the contractor, and the contractor's reputation. Do not base your decision solely on the lowest bid or because one landscape plan includes more plants than another does.