How to have objects appear in only one camera

I have 2 cameras, a minimap and a main screen.

I only want my waypoints too appear in the minimap. I put all the minimap only stuff on one layer since I figured that was part of it.

How would i go about that?

Yes, you use layers. Assign objects to layers as appropriate, and then adjust the culling mask for each camera so that it only renders the objects you want it to render.