Tips on hot to do a star trails shot.

I'm heading to camp tonight and hoping to get a night shot of the starts circling over the camp at night. Camera is a K5 so I'm looking for advise on how to set it up correctly.

Here's what I'm thinking so please tell me where I'm wrong or need to make changes.

• Mount camera on tripod firmly.
• Bulb mode with remote shutter release with lock feature.
• Thinking of 18-135 lens, or possible 50mm with 1.7 so it can be more open. Is the 50mm a better choice?
• Fresh charged battery.
• Length of time. Is two hours enough to get star trails?
• Do I need to worry about the camera over heating or anything odd?
• What's the best aperture and ISO setting?

Thanks for any advise.

Peteo