One of the common reasons for visa rejection is to not produce a legitimate financial support statement. Several deposit the needed amount for a very short window and then, produce the statement. Checking the passbook of a bank can easily reveal this. The best thing for students to do is to periodically deposit the needed amount and save it, without withdrawing. This should take care of the problem.
Others who may not have the capability to deposit such large sums of money should approach for a student loan at a reputed bank. Once approved, the bank will issue a financial statement that will suffice.
Students should remember one important thing. In my experience, some international students who come over to the US (after producing financial statements that say that they can support themselves), start pleading for support due to financial distress as soon as they arrive here. This does not gel well. Having produced an official document that you can support yourself and to state that you cannot is contradictory. Please try to avoid this.