mod ter is really easy to mess up, but I found some pretty good techniques that make it look nice
basically i use these bricks as guidelines for when i build with mod ter

wedges are good for carving out boundaries or small hills, and good for covering them too
for sloping mountains, use the flat to steep rule: start with 1/4 and work your way up, it helps make them nice and pointy
1/4 wedges make good grassy patches, they make for a decent filler to flat landscape
sylvanor's pine tree fits well with mod ter style, but that's just my preference
now if we combine all of those together...

you can put together something like this
just what i use, low detail and simple