This construction is very common in the GMAT. OG -11 has good questions on this. Off hand, I don't have the question numbers.
Generally in expletive construction verb comes before the subject. In other word, there is inversion in the subject-verb order.
Ex: There is an art exhibition at downtown.
In the above sentence verb “is” precedes the subject “art exhibition”.
The best strategy – as per Manhattan SC book – is to flip the sentence and check the subject and verb order.
Please refer following website: http://grammar.ccc.commnet.edu/grammar/concise.htm#expletive