What are the steps to efficiently replacing ones RAM? All I know is that you should buy RAM in pairs. I can look up my complete system information off of Dell.com so I don't have to worry about purchasing the wrong kind.

Currently I have four slots total, two are being occupied by x2 512MB RAM sticks. Should I purchase x2 1GB RAM sticks? Or another x2 512MB RAM.

Also, is there any trick to doing it, some sort of scan/defrag/partition(?) you should do before installing it?

Is 2GB good enough for most anything out, or should I go for 3GB or 4GB.