Lay out several fresh, disposable inkwell cups. Fill these cups with a small amount of the full strength tattoo ink. The more ink in the cup, the less dilution will be possible.
Add a small amount of distilled water to the ink and stir. This will create a diluted ink solution which is runnier. This technique is often used with black ink as it creates subtle gradations of watery gray shades.
Add a drop or two of white tattoo ink to any shades that you wish to lighten without changing the consistency. This method creates a lighter color. Be sure that you have created enough of the custom dilution to see through the completion of the design, as remixing shades can have uneven results.