to install RAM in matching pairs, with identical timings, from the same manufacturer.
If you buy a matching pair, it will be automatically configured as dual channel, start out with 'middle-of the-road', as sometimes when you try to pop in the fastest RAM, the problem of BSOD will appear (usually this is dealt with a few tweaks in the BIOS, but if you don't have to 'tweak' something, then don't).
Either way, you'll still have to probably upgrade the BIOS, as motherboards don't usually ship with the latest BIOS settings.
Hope this helps, and good luck with your build
I have recently purchased a Gigabyte 890GPA ? UD3H and AMD 965 Phenom 11 (125 watt revision)& Windows 7 64 bit OS. I'm not sure of the RAM to install. I want to start with 4GB. Question is, dual or single, 1066, 1333, 1600, or 1866. I will add more RAM later. I'm not a gamer but probably will try a few games that are on the market. Any thoughts or ideas would be helpful. Thank you!