Do not give a statement
Many times I talk with prospective clients and they are delighted to tell me that they have taken it upon themselves to go to the police department and give a statement after being arrested or questioned about a possible criminal case. This is a major mistake. You have the right to remain silent and should exercise that right. Do not think that by giving "your side of the story" that you're going to change anyone's opinion about whether you should be charged. Criminal cases are charged based on the evidence and the law. Often times, individuals give explanations for their behavior and do not realize that they have unwittingly offered potential evidence to the prosecution that implicates them further in the commission of a crime.
Do not rely on promises made to you by police
In the state of Florida, we have a system where the prosecutor's office (usually the Office of the State Attorney) makes the decision whether to prosecute a case. Not a "victim," the police, nor anyone else involved in the situation. Know your rights and do not rely on promises that may be made to you by the police at the time of your arrest or interrogation. The prosecutor is under no obligation to honor any such arrangement that you had with the police before they sent your case to the State Attorney for active prosecution. If you intend on cooperating with law enforcement, such as assisting in unsolved crimes, you need to do that through your lawyer and the prosecutor assigned to your case at a later stage.