he's/she's not into you..

You will notice the difference in his/her ways particularly in the way he/she deals with you. Like for example, the things that pleases him/her before does not please him/her anymore. There are ways of saving a relationship like a heart to heart talk, ask him/her to put things in the open. Maybe you can change for him/her. Spice up your relationship by doing other things with him/her. Take him/her on a nice vacation, a change in the scenery might do the trick.