How do I choose RAM?

I have a machine that's running with 1GB ram for a while and I've decided that I want to upgrade it. The problem is I'm not sure what to look for in a RAM card.
After searching for a while I found out that my computer can take DDR2 PC2-5300 memory. The problem comes in when I start hearing about latency and high/low density cards.:confused


So I'm left wondering two things at this point.
I know the lower the CAS/CL latency, the better the ram. But do I have to make sure the latency is within certain limits? Like, "Your computer is only compatible with CL 3-6 chips!", or can any computer use any latency?

My other question is how do I tell low density from high density chips?

I'm really new to tinkering with the hardware of my machines. ^^;

Thanks!

 

Go to Crucial.com and run their diagnostic, they'll give you some recommendations of what's compatible with your rig. I wouldn't worry about latency, # of sides etc. as you obviously don't overclock, only gamers and enthusiasts are interested in that.