I forgot to mention that you should also review the 'hand over' process from Sales Estimation to Installation Project Management. More specifically; are your estimators/sales people turning over useful and correct information to the Project Management Team to be able to effectively install the system.
Regardless of project size, I mandated that our Sales/Estimator Team assemble a document that contained a site diagram that showed travel time to site from office, proposed cable routes and device locations and also included relevant site and emergency contact information.
This document also included a copy of the proposal that the Customer purchased along with an individual page per device location that included pictures of the existing installation location and notes regarding the installation requirement (e.g. camera @ 14' from grade, conduit penetration through brick wall, xxx feet to head end, 'yyy' feet to power, desired view is 'zzz'.) and if relevant, a picture of what the camera would be looking at, IP address, device name, cable labeling scheme, etc.
This device location sheet also included any notes regarding 'difficulty' factor and what that difficulty may entail; e.g. need lift truck rental, concrete door jamb, existing device removal, 3-man minimum, escort required, etc. etc.
This document was reviewed in-house between the Estimator and the Project Manager assigned the installation and (if the project was big enough or sensitive enough), we would require that the Sales Manager, Estimator and Project Manager perform a site walk to review the project and ensure that everyone was agreed BEFORE any equipment was ordered or technicians scheduled on site.
If everyone on that Team agree after review of the Project document and a Team site survey, you've done everything you can possibly do to ensure you got it right.
There will always be something that comes up on a project that is unexpected. The object of this exercise is to reduce the number of 'oh sh*t' moments that your installation team experience during the installation that cause labor overruns.