How do I get mesh colliders to work?

Whenever I try to apply a mesh collider to my object, it does not work. I have tried checking “convex” but that doesn’t help either.

Does your character collide with colliders like a boxcollider ?

If not, verify you add a rigidbody on any gameobject with a collider who is moving in your scene.

Colliders work with Rigidbodies to bring physics in Unity to life. Whereas Rigidbodies allow objects to be controlled by physics, Colliders allow objects to collide with each other. Colliders must be added to objects independently of Rigidbodies. A Collider does not necessarily need a Rigidbody attached, but a Rigidbody must be attached in order for the object to move as a result of collisions.
http://docs.unity3d.com/Documentation/Components/class-BoxCollider.html

Nevermind, everybody. My problem is solved. I was using mainly models I made in Google Sketchup, and they were made up of smaller models. I applied mesh colliders to each individual model that comprised the bigger one, and it worked.

Make sure it’s not a trigger

My character does collide with box colliders. There appears to be a selection menu for the shape of the collider, but my object is nowhere to be seen in it.