Best Method of Creating Random Smooth Terrain?

When I spawn a brick I usually use the bricks around it to make parameters to where this brick can spawn, but this causes many issues:

1. Say I spawn from left to right. If I spawn my bricks in a back and forth manner using two for loops for X, and Z positions I will get just a slanted terrain.

2. If I spawn it in a spiral going out to in or in to out then it just creates a hill or a valley.

How can I spawn a random terrain without these kinds of patterns..?