With dating I think it is very important to be honest about your age up front. If someone is going to invest time into getting to know you with the hope that it might lead to a real relationship, they need to know how old you are. How many years can they expect to have with you? Are you of a reasonable age to have and raise children? Are you in school, in the workforce, or in retirement? Is there a noticeable generation gap?

While I dated women who were quite a bit older when I was young (I was 18; she was 36), now that I am 30 and looking to settle down and have a family, my priorities have changed somewhat. While I don't mind someone 5-10 years older, I do want someone who is still young enough to raise a family with me. By the same token, I want to date someone who is old enough to have finished school, established a career, and is ready to settle down and have a family. While I've never actually been attracted to anyone younger than me, I wouldn't rule out someone a few years younger. Age itself doesn't necessarily matter to me, but I do think maturity and stage of life are important if you are looking for a serious relationship. While I rarely meet anyone I'm interested in when out in public, if I do, I will ask about age up front because I'm really bad at being able to judge by looks. I also know that I appear quite a bit younger than I am and don't want anyone to be under the wrong impression. For instance, I'm a professor but I routinely get mistaken for an undergraduate student. I would hate to accept a date from someone only to discover later that they are the friend or roommate of a student!

Eta: if you're looking to date, why not try online dating or meetup groups?