gregbale
The late, great Shep Paine's book How to Build Dioramas is the single best source I've ever run across. It's concise, well-written (and well-illustrated)...and covers the gamut from groundwork to figures to all sorts of visual tricks that will up the visual interest of your project. It also has probably been the inspiration for something like 75% of diorama builders (at least of a certain age) in the hobby...
Second that! There's a whole library of books written since, but none of it renders anything Shep wrote obsolete or invalid. His is still the best, and a great book for beginners.
The first tip is to plan out your diorama. Sketch it out on paper, and don't worry about your drawing skills. The point is to start giving form to the picture in your head, and working from that. Show where you want vehicles, building, figures, vegetation, etc, to go.
And don't align your diorama with the sides of your base. If you're showing an airplane on the tarmac or ramp, for example, don't make any sides or edges of the concrete parallel to the edge of the base. If it's a vehicle on a road or path, or even in open country, don't line its sides up with the sides of the base. It will add visual interest.
And if you can't find a copy of Shep's book, you can still see the dioramas he built in the 70s for Monogram armor and airplane kits, here: http://sheperdpaine.atspace.com/
Shep wrote a tips brochure that was included in several kits. He expanded the basic content of the brochure into his book. And each brochure included specific tips, descriptions, explanations related to the kit and diorama in which it was packed. He also talked about problems specific to this or that diorama and how he solved them (like the Arnhem diorama). Many of us got our start when we were kids or teens in the 70s, from reading those "Tips on Building Dioramas".
Shep's goal was to show that any modeler with basic to moderate skills could do it.
And another site where you can see some of Shep's work is at BoxDioramas.com. Shep was a big proponent of box dioramas, dioramas installed in a case, with lighting, designed to present the story from a specific viewpoint. Here is Shep's gallery there:
https://www.boxdioramas.com/sheperd-paine
Don't be intimidated by his work there, but just look and enjoy it.
Good luck with your build!
Best regards,
Brad