As soon as you realize you are having difficulties paying your mortgage, it makes sense to research your options. Don't wait until it is too late and you must face foreclosure. Most lenders prefer to negotiate a solution in agreement with the borrower than to go through the process of foreclosure and many lenders will work with the borrower to complete a short sale.
Your first step should be to contact your lender and begin negotiations. Develop a budget to prove to the bank that you can make your payments, if the bank agrees to lower your payments.
The negotiation process begins with a phone call. Some lenders may want to wait a few months, before accepting your argument that you cannot maintain your payment plan. The mortgage crisis in 2007 may have alerted banks to pay attention and work with the borrower without wasting precious time. Your best bet is to have your lender provide instructions on how to proceed.
Even when working out a deal, you must understand the implications of a new payment arrangement and that you are probably not gaining much because a new payment plan may extend your loan out for a longer period.