Little things are the biggest way to show someone you appreciate them. Cooking a meal for them, buying them a small gift, can all add up in their minds to show them that you really care. Of course, a yacht and a brand-new corvette won't hurt, either!
Appreciation is a feeling that we all would like to feel or know every once in awhile. Saying you appreciate someone can be as simple as saying Thank You. You can also say I appreciate what you have done for me or I appreciate you.