Go where the wildlife you want to see is. Seems obvious, but certain destinations inside the country have much better wildlife (Osa, Sarapiqui, Tortuguero) than others. If you want to see a specific species (e.g. a quetzal or scarlet macaw or squirrel monkey) go where those are.

Choose smaller-scale lodging set in wildlife habitat. Big resorts with large swimming pools surrounded by concrete patios certainly have their appeal, but they’re not the places you’re going to see wildlife. Places that are low impact, set in a forest as opposed to strictly landscaped grounds, etc This will often involve a trade-off of convenience–a good lodging choice for wildlife will often be more remote and located far from town, restaurants, etc. But the reward is that unexpected sighting on the way to the parking lot, or the the lobby, etc.

Get out early. That’s when wildlife is most active in most places (exception being monkeys, which are generally active all day long). As daylight is breaking (5:30-6:30 am) is when you can see nocturnal animals making their way back ‘home.’ But,

Nature is unpredictable, and you should always be looking for branches moving in an odd direction, or the sound of something moving through the underbrush. Even when eating, keep your eyes on the trees and branches around you.

Talking scares away wildlife by alerting them to your presence (it also scares the wildlife off for others on the trail with you). Ditto with stomping on branches, twigs, and leaves. Also, often times you can detect wildlife through sound before you can see it–tropical vegetation is typically dense, and you’re not likely to see more than 20 yards in any direction without really concentrating on a specific area. In contrast you can hear movement and bird sounds from a wide radius around you.

Move deliberately, not quickly. Give your senses a chance to soak in the sights and sounds around you.