There are two main cleaning concerns with all espresso machines, the basket and strainer and, hard water. The basket and strainer get coated in coffee oils and can lead to a stale aftertaste. Hard water deposits can build up and seriously impact the flavor of your brew by clogging or limiting water/steam flow. There are many solutions from urn cleaner chemicals to vinegar to my favorite fix, cream of tartar.
Depending on how often you use the machine, once a week at home, put a tablespoon of cream of tartar in warm water to dissolve and pour it in the machine. Brew, without coffee of course, till water is gone. If your machine has a separate steam wand, be sure to use that as well. The beauty of cream of tartar is you don't have to rinse out the machine afterward and there are no chemical or vinegary fumes.