There are several approaches depending on your scope and complexity, but there a few key aspects I would consider:
1. Decide if you need (or want) aerial imagery on your site. There are a couple of good videos (Jared Banks did one that I found useful). This will add a life-like element to your site. Basically, you import the aerial and scale it, then add it as a surface to your mesh. I suggest this as a first step so I can elevate points and be aware of the imagery involved.
2. Check out the tutorials on taking a survey DWG and making your terrain mesh topographically correct. Whether by magic wand or manually, it will make for a nice graded site. Basically, the Pet Palette 'Z' values are set around and across your terrain mesh.
3. Consider if you need Renovation settings or phasing. This may affect some of your terrain modeling and other site elements to create existing and future views, etc.
4. If you plan to have more than one structure, consider a site model and hot-linking in each building. You will want to establish the story level strategy to accept these links. Personally, I created a 'Datum' elevation ASL along with my other elevations, then brought in each building relative to that level. (You will likely need to perform an SEO edit so each building 'seats' itself in your terrain; wherein your mesh is the target element.)
5. Consider contextual adjacent structures, even if any are available only in other 3D format for import. For example, in one study, I brought in a SketchUp model by another architect and I set it relative to my AC building model.
The above a just a few summary steps. I hope this helps.
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