Installing ram

i have been thinking about getting an extra 512 ram for my computer and my computer has 512 already i know its ddr and im getting ddr is there anything else i should look for before i put it in?

I think the speeds of the sticks should be the same. for example: PC3200. 3200 is the speed. I would do that just to be safe.

www.crucial.com/systemscanner

to be positive.

is better to get same brand speed and latency. also check if your mobo supports dual channel, then you'll want to install in slot 1 and 3 or 2 or 4. this is only if you have dual channel or 4 slots.