Establish an area of concentration within the broad field of landscape design consulting. Areas include: parks and recreation, transportation (airports, highways, waterways), healthcare facilities, school campuses, industrial or commercial sites, and housing subdivisions. Decide which of these areas attracts you the most and then tailor your consulting business to that segment of the field.
Write your business plan. Access and follow the standard business-plan design you will find online or at your local library. Compose it in a way that will attract investors, if or when they are ever needed. Include demographic information that shows your understanding of your target market(s). Demonstrate how you plan to convert that business knowledge into business success.
Legally register your business in the county where it will be located. Ask about all the legal requirements for running such a business and satisfy them before it opens. States will have different requirements and counties within each state will have different legal standards.
Recruit your contractors. Seek out the most experienced, well-known contractors in your area. Include also the lesser known, more eager installers who, like you, are trying to get established. Ask to see at least two or three completed projects from each installer before you hire them. Get direct feedback from their customers on how they were treated. Ask each customer to rank the installer according to the criteria that is most important to you and your business success.
Expand and diversify your consultation services. Incorporate into your services critiques of customers' current landscape designs. Offer new-installation checkups. Plan and teach horticulture classes about planting, maintenance and soil types. Offer free tips and guidance to all those with less than a "green thumb." Announce and give to the public free landscape design seminars. Establish yourself as the resident expert in your area of concentration.