In my experience, the most common way people are arrested for possession of marijuana is during a traffic stop.
A traffic stop can happen for several reasons. Typically, the cop witnesses a traffic infraction, such as speeding or failure to maintain a single lane. Other times, the violation may be for equipment, such as illegal tints or a light that is out.
Whatever the reason, a traffic stop is an opportunity. An opportunity for the cop to stop you and to have a look around.
Now many things may happen. The officer may smell marijuana when he or she approaches your driver's side window. If they smell marijuana, they may lawfully search your vehicle. That is Florida law.
The officer may see marijuana through the driver's side window. This is known as the "plain view exception." If a cop sees marijuana in their plain view, they can search the car and arrest you for possession.
Another way cops find marijuana is simply by asking. They may ask, "do you have any drugs or weapons in the car I should know about?" If you say "yes," they may then ask to search the car. This is known as a consent search.
I have noticed that cooperating with law enforcement officers is a double-edged sword. On one hand, your cooperation may lead the cop to issue you a promise to appear (PTA), or a criminal citation. This is still a legal arrest but not a physical arrest. On the other hand, you may have consented to a search or made a statement. These two actions could hurt your case.
But if you don't consent to a search or do not make a statement, the cop may handcuff you and take you to jail. You will be punished for exercising your rights.
What you do when the cop is standing at your window is your call. Some people would rather cooperate than spend a night in jail. Others would rather hang on to their rights, no matter the cost. I cannot advise you one way or the other.
What I can tell you is that anything you say will be used against you. As well, if you consent to a search, you waive your constitutional right against an unlawful search and seizure. So unless that consent was not voluntary (meaning that the cop held a gun to your head and made you agree to the search), you will probably not prevail on a motion to suppress.
If you are driving in Miami-Dade or Broward and you are stopped with marijuana in your car, give me a call. You will likely want the services of a criminal attorney who handles possession of marijuana cases. This is because possession of marijuana is a first-degree misdemeanor in Florida with a maximum penalty of one year in county jail. Also, a conviction (adjudication) to this charge will suspend your driver's license for one year.