A useful way to hone in your deductive tasting skills is by comparative tasting. These comparative tastings can be conducted in multiple fashions: open, single-blind, double-blind, etc. Our favorite practice is single-blind, as this allows you to approach each theme methodically while still testing one's deductive tasting skills. 
 
Another tool to use is a voice recorder. Record your tasting, go back and listen to your tasting, and take notes to learn your common descriptors for your testable wines. As you compile more data on each wine, your knowledge about how you taste will increase, and the more proficient and consistent your tasting will become.