Don't let soap cleansers dry on the sink's surface. Rinse regularly to keep the chlorides found in most cleansers from affecting the natural luster of stainless.
Steer clear of steel wool pads. The iron particles that are left behind can lead to rust and corrosion. For hard-to-clean projects, try a ScotchBrite scouring pad when the job at hand requires a little extra effort, again in the direction of the grain.
Avoid leaving steel and cast iron cookware in your sink for extended periods of time. Iron plus moisture on top of stainless can lead to surface rust and staining.
Rubber dish mats, wet sponges and cleaning pads are a no-no for a lengthy stay in your sink. Since they trap water, discoloration and staining can result.
Just as you don't use your cutting board to clean the dishes, don't use your sink as a cutting board. Knives and other sharp kitchen instruments will naturally damage the surface of your sink.
Avoid prolonged use of chlorides (such as chlorine bleach), bromides, iodides, and thiocyanates on stainless steel surfaces as these chemicals will cause pitting, corrosion, and metal discoloration. Allowing salty solutions to evaporate and dry on stainless steel may also contribute to corrosive conditions.