The motherboard is the most important component when you are building your own computer. You need to make sure that your motherboard is compatible and can support all of the features that the other components might have. But don’t worry, I will explain all that you will need to know when buying a motherboard.

What Processor Socket Motherboard Do I Need?
You need to make sure that the motherboard will support the processor that you want to use. Fist choose a processor and find out what socket the processor is. There are really only 4 different types of processor sockets, For AMD you will have socket 754 and 939. For Intel you will have socket 478 or 775. When new generation processors are released they are likely to use a different socket number.

Dual Core / Hyper threading Support
Don’t assume that all motherboards will support dual core and hyper threading processors. Virtually all AMD socket 939 motherboards will support dual core, make sure you check before selecting a motherboard. Dual core has become very popular these days, so its quite important to get a dual core motherboard.
 

Forward Looking Processors
If you are building a top of the range system then it might be worth keeping an eye on what processor speeds the motherboard supports because in a few months after you buy your system you might want to buy a faster processor to get that little extra boost out of your system. Some motherboards at release might only support a processor speed up to say 3.2gig, but make sure you check the motherboards website as BIOS upgrades are released which will possibly support a faster processor when installed.
AGP / PCI-E??

You need to check what form your graphics card is. It will be either AGP or PCI. Make sure that your motherboard has one of these slots available. Also AGP / PCI will run at certain speeds, make sure the motherboard supports this speed. For example I might have an AGP x4 speed graphics card, I need to make sure the motherboard has a slot that can support AGP x4.

Dual Graphics Card Or Not?
If you are building a top of the range gaming system, or you want to use your computer for heavy graphics use then you might want to use 2 graphics cards. It is possible to install two graphics cards and have them act as one, This will spread the load between them and let you achieve a far higher frame rate than you ever could with a single graphics card.

Sata Support?
I would recommend buying a motherboard that supports sata devices.  Sata hard-drives run at a much faster speed than IDE hard-drives so you will get a general speed benefit from using Sata instead of IDE.How Many PCI Slots?
You will need some free PCI slots. PCI slots are used for devices such as, sound cards, network cards. Always make sure you have a spare PCI slot, if you don’t think you will need some now, you might need a slot in the future.

How Many USB Slots?
You will need to consider how many USB slots you need.  Think of what devices you want to connect to your system.  USB slots are usually located at the back of the PC and at the front,  typically there will be 1 or 2 USB slots

Do You Want To Over Clock Your Processor?
I would not recommend doing this as you risk breaking your processor.  But if you want to over clock your processor there are some motherboards that were specially made to do this job. Take a look at a few over clocking motherboards here http://www.devhardware.com/c/b/Motherboards/

Raid Support?
Do you plan to use raid?? With raid you can merge many disks in to one large disk and also add redundancy should one of your drives fail.

Onboard Audio?
Some motherboards have audio ports integrated,  These ports are okay to use but if you want surround sound you will need to buy a separate PCI sound card and connect your speakers to this.

My Recommendations and Why,,,
Entry Level System
For the entry level system I would recommend you buy the cheapest motherboard you can find that supports your processor. Also make sure you get onboard graphics and sound as this will save you a bit of money.
Mid Range System
I would recommend you buy any mid range prices motherboard, just make sure it supports all of the features you need. (Processor speed, Dual Core, Graphics card connection type)
Top Of The Range System
Buy a motherboard that supports your processor speed and then some. If you want to upgrade in the future you can with out changing the motherboard, which can be costly. Make sure the motherboard can support 2 graphics cards and has 4 memory slots which support dual channels.