It depends on what your needs are. If you're looking for standard run of the mill fixed cameras, I would recommend Hikvision without question. If you're going the PTZ route, while I've never personally worked with them, I'm told Huisun has better offerings in terms of value per dollar with respect to feature set.
When it comes to outdoor cameras, avoid bullets like the plague. It depends on your region for the most part but I learned the hard way when I met my match with the itsy bitsy spider:
Spiders cannot easily build webs on a hemisphere, whereas bullet cameras have vertices that make it easy.
While I stick with Hikvision embedded NVRs, BI is great when going the PCNVR route, and honestly offers a lot more (that I personally don't need), but for the cost of a license and a decently built computer, it's well worth it.
As far as PoE is concerned, you said you have 12 cameras. Too many for an 8 port, so you'll need a 16 port PoE switch. The problem with most PoE switches you will find is that they are not all PoE ports. A 5 port PoE switch only has 1, an 8 port has 4, etc. When you go to purchase this, be absolutely certain that all 16 support PoE. Normally I would say make sure you get a PoE switch with a trunk/uplink port, because this will allow you to use all 16 ports for cameras (running at fast Ethernet speeds), and have 1 trunk line (running at gigabit speeds) back to the recorder. In your case, if you're absolutely certain you won't go up to 16, then an uplink port isn't explicitly required. That's more of a best practice thing.
When wiring, be sure you are purchasing Pure Copper category cable. If you see anything listed as CCA, copper clad, or any box (1000ft) that is well under $100 per box, avoid it. Copper clad is a mixture of aluminum and copper (it has an aluminum core and a copper outer layer, or skin). It is not nor will it ever be UL listed or permitted by the NEC, aluminum has a higher resistance value, so with PoE it means a *theoretical* greater fire risk, especially over longer distances with a more significant voltage drop. Aluminum also has horrible tensile strength vs copper, so the wire does not take bends and kinks as generously.
With all of this being said, I have installed about 10k feet of the stuff, all of which is still functioning perfectly fine to this day. Mind you this was before I had any idea that they were sneaking aluminum in. I jumped at the price, but obviously too good to be true. Am I going to go back and replace it all? Absolutely not. That's an excessive amount of labor for nothing. However, going forward I know what to look for. The cheapest box of pure copper I've found was $90 for a 1000ft box of Cat6. Purchased and verified, it's the real stuff. Your box will also have a hologram UL sticker on it if it's genuine. Simply printing the UL logo on a box of cable anymore is no longer acceptable. It's too easy to forge and has been done so and continues to happen. This went into effect October 2010:
http://ul.com/wp-content/uploads/2014/04/ul_HolographicCableLabels.pdf
You can get away with
Cat5 or 5e on the cameras because it's only running at 10/100 speeds, but for the NVR and any of your core networking, Cat6 all the way. I would also recommend a basic gigE switch to keep your Camera traffic with your NVR away from your router and main network. This is another principle/best practice thing that if you didn't do it, things would still work, but I personally like to give my router a break from non-stop traffic if it isn't absolutely necessary.
Hard drives on your NVR, get WD purples if you can. Very reliable.
I'm out of other things to think of, this is a good start at least.
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