Manny, as you have already seen, you ask a question and you can get a good deal of varied answers and approaches.
Having previously done the hi-rail approach (ballast, added ties, ground foam, etc.), for my current layout I opted for what I jokingly call the "low-rail" approach. I browsed local paint stores until I found a discounted mis-tint can of paint that was a grey-ish color. I painted the entire layout surface with this color, which was going to be my track ballast.
I then played around with layout configurations and when I finally was happy, I used just enough screws to hold things in place. This is to help reduce noise transfer. I then cut ties out of brown foam material (I'm using 027 track) that is sold at places like Hobby Lobby. Although the foam is thick enough to stay in place below the track, I still used a glue stick to place all the foam ties. This greatly cuts down the noise rumble from the board surface.
Then I went around the layout and trimmed off the grey "roadbed" with a base green paint (you could use brown instead), and painted the remaining open spaces.
Now at my leisure, I have used small containers of acrylic paints in various ground to add more "detail." Areas around a factory or yard will have more brown colors, whereas areas around a train station will have a more manicured look with just a couple shades of green.
And if I don't like something, or decide to change buildings, I can just paint over that area, versus having to scrape up ground foam and scenic material.
I also have a number of items designed to be moved around, since I have a small layout, which could potentially become boring. So being able to move some things around keeps things interesting.
Like for example, the Lionel Girder Bridge, that has a sheet metal base that goes beneath the track. Instead, I mounted the girders to a couple strips of wood painted to look like a walk way. These can be easily set down on the layout right next the track. And I can easily replace the Girder Bridge with an equally altered Lionel snap-together Truss Bridge. Many of my trees are mounted in bases made of air-dried clay that I painted, so that I can move trees around at will.
Animated accessories take up a lot of space usually, so I have an elevated stretch of powered track at the back of the layout, where I have a number of operating train cars. To easily turn on or off the operating cars, I have strategically placed a narrow piece of a sipping drinking straw over the center rail where the pick up rollers on the car are located. Then, a simple move slightly to the left or right turns on the operating train car. Move it back and it is turned off.
So there are lots of creative ways to do a layout. There's a general thought about layouts that bigger is better. Not necessarily. I think more thought out, creative layouts are better.