Take pictures
Take as many as possible so as to enjoy the beauty long after you have left.
Hire a guide
The guides know the animals' habits and are able to tell you where the tapirs normal routes are. however, be sure to also make sure to take the time to explore on your own.
Visit La Sirena
In fact it is recommended that you spend as much time as possible here since it makes a good central base for exploring the park. it is located 20km from each entrance.
Kayak
Ask the locals for a kayak ride through the rainforest.