Easy...just kidding. It is typically not so easy or even possible, but it does happen. Here are the most common ways a case may be dismissed:
Evidence-Related Dismissal:
Lack of probable cause, illegally obtained or insufficient or lost evidence, unreliable witness, etc.
Constitutional or Procedural Grounds:
Violation of legal rights, statutes, or procedures by the state, ie, incorrect charges, etc.
Prosecutorial Grounds:
Prosecutor misconduct, like a Brady violation or unethical action. Also, a lack of witness or AV cooperation.
NOTE: Sometimes people think that if the "victim" does not show for trial, that the case must be dismissed. This is not always true because the criminal case is brought by the state (not the complainant) against the defendant. Remember, the DA represents the state, not the AV/Complainant. With no AV the prosecutor still may determine their case is strong enough to proceed. Now, this is not always a smart path and many counties (maybe most) will never prosecute without an available AV. Also, if the AV is a CI then the DA may have a real challenge on hand. The Sixth Amendment is clear that you have the right to face your accuser which does apply to most criminal cases.
Court Agreement:
This can include a completion of a diversion program or some other conditional program, commonly determined in a plea agreement.
Other Methods:
Exculpatory Statement - Commonly we will obtain a dismissal via an exculpatory statement from the AV (complainant) that in some way requests a dismissal due to further identified actions, conditions, clarifications, or explanations of the incident or case. The defense investigator is typically the intermediary in the process and the defense attorney then presents this new exculpatory evidence to the prosecution.
Civil Compromise - This is an agreement that applies to many misdemeanor cases. The agreement is a negotiation between the AV (the injured party) and the defendant. The agreement is super cool because it takes the case out of the criminal track and moves it over to the civil track. This process circumvents the DA with power to dismiss only in the hands of the court (judge). This can be a tricky negotiation and process, but is very effective and rewarding. It has the advantage of moving the case quickly, reducing cost to the system, and not leaving a charge that otherwise may be on the defendants record. Satisfaction can be creative including repair, replacement, financial satisfaction, or even an apology letter. The civil compromise is an agreement between people, not the criminal courts. The defense investigator is typically the intermediary in these cases.
In a civil compromise, the final decision-maker is the judge, but I have yet to have a civil compromise agreement rejected...yes, challenged by the DA, but not rejected by the court. The charges in the case have to meet certain statute rules, which vary by state, in order to be eligible for a civil compromise. The case must be analyzed to determine eligibility prior to beginning the agreement process.
Personal Note: I recently completed three of these agreements with two different attorneys in two different counties in one week...which was super rewarding!
As you can see, this is why you need a legal team to support you and your case. Provided above is experiential and practical advice only, not legal advice. Contact your local attorney for the experienced legal advice needed to negotiate through your local and state rules and laws.