pcpartpicker.com will give you compatibility lists.
You're probably going to want a Micro-ATX.
If you want to use it for SLI look for two PCIe x16 slots (really hard to find two on a Micro-ATX.)
Make sure that you can get plenty of RAM, maybe it only has 2 DIMM slots but how much will they support, sometimes you can find a motherboard with 2 slots that supports 32GB and another one with 4 slots but it still only supports 32GB.
When considering RAM check two things
1. The speed (DDR3-1600, DDR3-2000, DDR3-2400...) you don't want to go to high, 1800-2400 is a good range.
2. The CAS (11,10,9...) the lower the CAS the faster it is.
When you find one that you like check the reviews, some people will just be complaining, but if more than half of them are then you probably don't want that motherboard.
Whatever you do DON'T GIVE UP it's confusing but if you keep at it you will be able to figure it out (I only got into this in the last week.)
Here's a guide
http://www.tomshardware.com/reviews/motherboard-selection-guide,3900.html