OH Lordy (:< 0
Details come in 2 types: design and construction.
Things like visible mortise and tenon joinery or dovetails, dowels, wood grain variations or complements, book matching panels etc are construction methods that add detail and personalize the project. The overall size and proportions are independent of these details.
Design "details" are more like the proportions of the major pieces, the use of glass or other kinds of panels, the light vs dark of stain or colors, contrasts of materials like wood/stone/tile either for accents or they can be integrated into the design itself. What's the design/piece look like in other words....?
So, you start with a basic design with the sizes of things, like drawers and spacing etc, the choice of materials in the various places, then add the construction details to that design.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)