If all you are doing is putting in another stick of ram, you just have to be careful, nothing to "watch out for".
Earthing is to remove the static that your body may be charged with. Most, including myself, simply turn the power off at he wall socket and leave the cable attached to the PC. Then, after touching the metal parts of the case, fit the ram. By doing this you are using the case to discharge any static you may have.
In all, five minute job and most of that is undoing the case!!