The first thing to consider when implementing a do it yourself security camera system is where the cameras will be placed and how many cameras will be needed.
What capabilities do your security cameras need in terms of resolution, night vision and weather-resistance? Most packaged systems come with adequate general purpose cameras.
There are several choices for recording surveillance footage - stand alone DVR, DVR Card, DVR Converter and SD Recorder. Your choice should depend on your budget and the functionality you need.
The main types of video signal transmission are Wired, Wireless and IP Ethernet. Make sure you to understand the capabilities of each.
How are the security cameras going to be powered? Even wireless security cameras need AC power.
Careful mixing and matching security cameras and DVR's. The cabling and connections may vary from one vendor to another.
With DIY security camera systems, technical support is very important. Choose a vendor that can accommodate your support needs.