It is difficult to answer this question without more information. There are certain legal issues which, if you respond with them, provide defenses to the Complaint which the lender then must overcome in order to complete the foreclosure. Unfortunately, it is unlikely that borrowers can do this successfully on their own. When people file their own responses, they generally admit the debt and ask for more time, explain that they are having financial problems, or are trying to do a short sale. Unfortunately, raising these things do NOT defenses to foreclosure, and actually make matters worse, since they are acknowledgment by the borrower of the debt and the delinquency.
Valid defenses relate to either disputes of the debt (i.e. wrong amount), legal standing to sue (this is often an issue these days, where you are sued by an entity you have never heard of before), and other attacks on the indebteness. An additional category of defenses is what are called "affirmative defenses". While Clerks of Court in Florida often tell foreclosure defendants they can file their own response, it is a serious mistake to try. While it is permissible for people to defend themselves, without knowedgable guidance, you will probably make matters worse instead of better.
It is also of CRITICAL importance to know that you only have 20 calendar days after you are served with a Summons and Complaint to respond; after that, the Plaintiff can have a default entered, and then proceed to get summary judgment and a foreclosure sale without further notice to you.
There are knowledgable attorneys who will assist you in defending foreclosure on an affordable fee basis. Please don't try to do this yourself - it is like trying to do your own brain surgery.
The National Association of Consumer Advocates maintains a directory of attorneys all over the US who work for and in the interests of consumers. In our practice, we evaluate Summons and Complaints in Foreclosure for people at initial consultations without charge. But, beware - there are many "rescue scams" that also exist for the purpose of capitalizating on people in foreclosure.