Our approach is very simple. It's trivial to make a fully saturated (100%) water solution. While we are using salt the same approach may be used with other soluble compounds to produce of variety of chemical dilutions.
Once you have a bottle of saturated solution, you can take a portion of it and dilute it down with distilled water (or even tap water if it's not important to be too exact) to any percentage ratio you desire from 1% to 99%, but you need to start with 100% solution in order to mix an accurate dilution.
While I will focus on common table salt the same techniques can be adapted to any of the inorganic compounds in the later step.