Your age and your occupation are important. Your hair and eye color probably aren't. If you are not willing to travel far for a date, where you live might also be worth including. If you have any strong interests or characteristics that help define you, include them in a concise manner. If you're a vegetarian, a sports fanatic or Sabbath-observant, that could be important.
Some physical characteristics can be important.
If you are a 6-foot woman looking for taller guys, put that in the ad. The object is to give the reader a little taste of who you are. If a potential mate's age is important, put it in the ad. If you can't stand to kiss a smoker, be sure you write that you are looking for nonsmokers. If you don't want or like children, readers would probably want to know that as well.