Constant recording or motion detection? 
 Do you want to see everything the cameras see throughout the day and night or would you prefer them to be set on motion detection so they record only what moves past them. Motion detection allows for greatly increased recording capacity on the DVR. 
For example if the your front door camera   was set
 up correctly with the motion detection setting, you would only see who 
  had come to your front door throughout the day with out having to 
manually wind   the DVR forward. 
How do I backup my Footage? 
The recordings can   just tape over the old footage after 30 days or so 
or you may want to back them   up to CD, network PC or USB. These 
choices will all affect the budget for your   home security CCTV system.
            
How do I choose the correct camera for my   application?
This in general is a comparatively 
difficult decision. Many aspects of the   installation must be taken 
into consideration in order to obtain the correct   performance that 
meets your requirements.
A high resolution camera should be 
considered where greater detail of scene   is required. E.g. Colour 460 
TVL, Monochrome 570 TVL. Choosing a more sensitive   camera will improve
 reproduction in poorly lit areas. The sensitivity of a   camera is 
indicated by the minimum amount of light in order for the camera to   
produce a usable picture. e.g. Colour 1.0 Lux at F1.2.
A conventional camera produces a pale 
backdrop when an object is shot against   a bright background. BLC (Back
 Light Compensation) will counter strong light   sources retaining 
picture quality.
Concentrated light sources directed 
towards the camera (e.g. car head lamps)   can be inverted by an 
optional peak white inverter or an eclipser function. This   has the 
effect of bringing detail to areas and making an object clear, that   
would otherwise be shadowed.