There is one cup on the window.
There are three cups on the window.
There is a cat outside.
There are many cats outside.
The trick to choosing the right verb is to find the real subject of the sentence. Sentences beginning with "there are" and "there is" are using a different kind of sentence structure called an expletive construction. You can get a sense of how expletive sentences are different from the more common subject-verb sentence structure because if you swap in another noun for the word "there," the meaning changes.Via: Grammar Girl
Although I believe people often take this suggestion to extremes, many sources say that expletive sentences are bad style and should be avoided, and you can see from the example how easy it is to get rid of the word "there" and rephrase the sentence.
"There is a couch and a coffee table in the room" easily becomes "A couch and a coffee table are in the room." If you want to go wild, you could even use a more descriptive verb and write, "A couch and a coffee table *sit* in the room," or "A couch and a coffee table *grace* the room."