The first step in designing this recently-commissioned table was to make a full-scale mockup to get the dimensions just right. In this case, the height of the table is 29-1/4", and has a 59" diameter. When designing a piece, I use a sort of "back and forth" method: I go from initial sketches, to a mockup (for basic dimensions), then back to sketching for details, then to dimensioned drawings. If need be I'll create full-scale mockups or "studies" for particular details, to see if they will work with the rest of piece, or (and this is usually the case) to figure out how to build it. This method works for me, because it allows me to experiment with the design as I go, while still maintaining some basic perimeters to work from.
In order for the table to have just the right "feel" for the client, shims (in this case, some MDF and wood scraps) were used to adjust the height of the tabletop. With a base height and diameter established, dimensioned drawings can be produced.