Be/look very professional.
Apartments, speak with manager on duty, you may be referred to a property manager or company that handles those affairs.
Sub-division entrances, ask some of the home owners for info about their Home Owners Association, who to contact, etc.
Be prepared in either to submit a written proposal/bid after you have walked the property and been told exactly what services they want to be included. Get very detailed about it. Do not take their word on physical size of property, walk it with a time-it-will-take-to-do eye, take notes, don't leave to memory.
Don't just mail in the paperwork.
If at all possible, when all is prepared, ask for a brief meeting with the person(s) that make the decisions. They could be located out of town for commercial properties.