1. Work from photos. I’ve compiled a big trove of photos from the area and season (both are key) that I’m modeling:https://picasaweb.google.com/103328750375507168249/WinterSceneryReferencePhotos. I’d recommend doing the same for your own interests. Railpictures.net has plenty of scenic stuff that should get you started if you can’t get there yourself (and it’s tough to take photos of June in January).
2. Pay attention to details. Note the things that are present in photos that your mind might be taking for granted. Things like ROW profile, the structure of a forest (leaf litter=>shrubs and small trees=> trees), access roads, rocks “working”, the color of things (gray trees, not brown, the real color of asphalt, etc…), guard rails, man made detritus are key to getting it right.
3. Pay attention to scale. The real world is big. I know it seems like a simple fact, but people often overly miniaturize scenery to fit more in. Fewer, but bigger trees is the big thing here.