The common rule for any break room is that employees clean up after themselves, but offices will usually have a professional crew come in every night to mop and whatnot. Either way, you want to make sure you have proper cleaning supplies in stock to keep the lunch room spotless.
Take note of the types of surfaces and materials that are in your break room and acquire the appropriate chemicals to kill germs and protect the visible surfaces from corrosion. Multipurpose cleaner is good for most things, but if you have a lot of glass or polished metals, a more specialized cleaner may be in order. Any job requires proper tools, so make sure you have enough brushes, sponges, sweepers and brooms to make cleaning the break room an easy task.