well you need to match the cpu socket on the board to that of the processor. the current gen intel processors use LGA1150, current gen amd uses AM3+.
for a discrete graphics card you will need 1 PCIex16 slot. All boards provide the same amount of power through the slot, if the card needs more(as most mid to high end cards do) there will be connectors that will need to be connected to your power supply
RAM is pretty standard DDR3 1600 is supported on almost all boards, voltage should be 1.5 its the most common voltage for ddr3.
a 600-700 watt PSU with an 80 plus certification will provide enough power to run most configuration with a single graphics card. if you want to add a second get a larger one like 800Watts or so