what to consider while writing SOP and SLA of data center

my company has decided to outsource the data center to another company for which I need to write both SLA and SOP of Data center services, the other company will be providing us the hardware, space (Racks), power solutions (both primary and secondary supply)security of data and equipment. the services running on the hardware will be our responsibility hence i need some help. what are the factors that I should consider while writing any such SLA and SOP.