Have enough operating capitol to survive for a year without making a profit.
Pay for as much as possible with cash...don't finance anything unless you have no choice.
Get your licenses, DOT's, liability and vehicle insurance as well as insurance for secured impound yard.
Find a local mechanic that you can trust to repair your trucks quickly when needed. When your truck is down, you are not making any money. Inspect your trucks weekly and perform preventative maintenance routinely to try and avoid unexpected down time.
Find out how your local police operate their rotation list and get on it.
Sign up as a vendor for every insurance company and roadside assistance company you can find. Some pay better than others, some don't pay at all. Weed out the ones that are not profitable.
Set up a Square Up account to accept credit cards on your Andriod or iPhone. A lot of folks don't carry cash.
Get professional looking uniforms with your company name and logo. Wear them everywhere. Make sure trucks are all lettered alike, including your personal vehicle. You're after name recognition. The more people see your name and logo, the more they will remember it.
Set up a clean, one page web site that is mobile friendly. Learn or pay someone to SEO it so that it shows up on the first page of Google, Bing and Yahoo. Nobody uses yellow pages anymore for emergency services.
Drop business cards at every restaurant, gas station and auto repair shop in your area.
Hire an accountant that specializes in small businesses. They will be your best friend or your worst enemy. They can make you or break you.
Pay yourself a fair, living wage for your area. If you are not able to do this, talk with your accountant.
Talk with your accountant and get the to help you decide if you need to be incorporated, an LLC or DBA. There are advantages and disadvantages of each. Get your accountant to explain the differences and decide which is best for you.
Don't expect to work 9-5, mon-fri ever again. You will never be able to plan anything with your family again. Be ready to work when the call comes in. If you plan on going out, the phone will ring on your way out the door or when you are out eating dinner with your family.
You might think that you are working for yourself. In reality, you are working for your customers.
Enjoy it. Owning a small business can be very rewarding, but can also be a huge strain on your family if they are not behind you 100%.