Beginner hardware
IP Cameras (2010 and newer)
The best, first advice is to check that your camera is compatible with zoneminder's motion JPEG (MJPEG) or H264 via RTSP.
You should read the Documentation. The developers spent and continue to spend a great deal of time writing it... you should spend at least a little time reading it. Specifically, read the part about shared memory.
Recommended IP cameras
Axis brand cameras are a good choice, but expensive.
Hikvision cameras have decent quality and are more affordable.
Generally speaking, any camera that is ONVIF compliant will work with ZoneMinder. The differences between a more expensive camera versus a cheaper camera is how well it performs in non-ideal lighting conditions. If your camera is in area that is always well (and evenly) lit, then that too-good-to-be-true super-cheap 1080p IP camera, might work just fine. On the other hand, it might look terrible at night or if part of scene is under a shadow. It's these kind of performance features that are hard to determine ahead of time without physically testing the camera.
Analog Cameras (pre 2010's)
The best beginners hardware and setup is to use an old unused system, anything from late Pentium 3 or Athlon XP generation of cpus will be more than enough for a setup capable of running 2 or 3 (analog) cameras depending on configuration.
You will need one of the cheap pci cctv capture cards from Ebay that use the bt878 chip, if you search for pci cctv on ebay then most of the cheap cards that show up will be a card of this type, see the Pico2000 section of the Zoneminder wiki for a few photos of these cards and a little more technical information. For capture cards with tw6800 chips you have to compile the driver. Have a look at KesCom PG104 for instructions.
You can alternatively buy them and better boards from the retailers in the shop section of this webpage.
You will need to configure the capture card as described in the Pico2000 wiki
Another (possibly better) option is to purchase a standalone IP Video Encoder. see Hardware_Compatibility_List for more details.
Next source some standard analogue cameras from the retailers listed on this page or any other source you like.
Install Zoneminder using the CentOS guide contained in the wiki or any other distro guide you are happy with, I personally started with the CentOS guide and it has worked well for me.
Ubuntu and Debian are the easiest to setup, and best supported. Beginners are advised to use those.
This is of course a beginners system and so can be expanded and improved on once you are happy, my aim in this design is to build a Zoneminder system as cheaply and basic as possible, I have made a lots of setups that are still operating on the above basis.
Note that analog cameras (not ip cameras) have resolution limitations, so if you need/want high res, you will probably want to use ethernet and ip cameras, not analog and coaxial.
