First provide a solid explanation of as to how, you have landed yourself in hardship. For example, how your financial condition is right now compared to when you first obtained the mortgage. Mention as to what you have been trying to do, to make ends meet and are still not in a position to make your monthly payments.
Next tell them about the condition(s) that has caused your financial hardship. Lenders tend to accept the following aspects as justifiable reasons for hardship, although there are many more, which they also accept: Being unemployed, Death of a family member/spouse, Job relocation, as well as unexpected medical bills.
Lastly you need to ask for what you are trying to accomplish. Do you feel you would like to try to stay in your home and just need a modification. Or is the situation too far gone to work it out and you would like to ask that they approve a short sale.