depend what come with your system, you could have one 2Gb ram stick installed and a spare slot. You can either go with putting a 4Gb ram stick in the spare slot to get 6Gb or simply replace what you got with 2 sticks of 4Gb to get 8Gb total. Make sure you get laptop version of DDR3 ram. desktop version are not compatible.
and also there is on every importanrt thing. when i see ram usage in processes i see Chrome alone is sucking more than 1 GB of my RAm. what d *** with CHrome?
all web browser, chrome, firefox, ie, are all memory hog, especially when you have multiple web pages open.