There are two broad categories of stain: dye that is dissolved in a liquid, and dye and/or pigment combined with a binder. The first are usually called “dye” stains and are sold either as powders for you to do the dissolving, or are already dissolved in a liquid solvent. The second are often called “wiping stains,” “pigment stains,” “oil stains,” “water-based stains” or “lacquer stains” and are the common stains you buy in cans at home centers and paint stores.
If a dye stain gets the wood too dark, try removing some of the dye by wiping with its solvent. The powder dyes labeled Lockwood and Moser (which are the same) are easier to lighten than the liquid dyes labeled “NGR” (non-grain-raising) or Transtint (which are also the same; Transtint is just concentrated).
If a pigment or wiping stain (those that contain a varnish, lacquer or water-based binder) gets the wood too dark, try removing some of the color by wiping with the thinner for the stain or with lacquer thinner or acetone. These stains are much more difficult to lighten than dye stains.
In both cases, you can also scrub the surface with steel wool or a synthetic abrasive pad together with the solvent or thinner for the stain to remove more color. Try to keep the scrubbing even over the surface so you maintain a roughly even color overall.
With dye stains, you can usually bleach out most of the color using household bleach or swimming-pool bleach. It won’t be possible to remove all the color, however, without many applications, sanding between each.