Does anyone know how its possible to record indoors and reducing the echo as much as possible?

If possible, choosing an interior that doesn't have a lot of echo is a good place to start. Steps can be taken to reduce the echo in a room also. It is a common practice to hang blankets in the room.

It is crucial to use a directional microphone, and to have it less than two feet from the mouth of the person speaking. It is not possilbe to get good results with a camcorder's built in microphone from the distance you usually shoot video from.

What do you have for equipment?

If you do a search, you'll find a lot written about that. First thing, never use a shotgun in a reverberant space. Use a good hypercardiod as close as possible. Blankets can be really helpful, but you need a lot of them. Hanging does a lot more than putting them on the floor.