   Terrain Rendering Advice
  I've just started planning out a game and terrain will play a large part in the game in general including graphics, gameplay, etc.  Therefore I've decided that it would be a good place to start considering how significant it is to the finish product.  I've heard techniques like geomipmapping, geoclipmapping,  and ROAM thrown around and I'm wondering what techniques are commonly used in modern games.  The geometry for the most part will be rolling hills with not a lot of mountainous regions, just incase that might affect the decision of what to use.   
  You wont need to worry about terrain optimization for a while. You can use static geomery at a very high polycount for a long time. It depends on how big your terrain really is.   ;  +1 to what dpadam450 said.  For reference, I'm using a 64*64 square grid of vertices, comprised of 8192 tris, without any performance issues, using 4 textures.  The world appears quite large, while also appearing smooth and detailed.  The real performance impacts I'm getting are any CPU->GPU data transfer call overhead.  The grid layout also makes collision detection/pathfinding a sinch.   