The most conventionally appropriate age to start dating is at 18 years. This is the appropriate age to start dating because by then, you are mature enough to overcome emotional vulnerabilities that come with dating. Dating incorporates bliss and hurt in equal measure mostly and hence beginning earnest dating at an earlier immature stage is setting yourself up for a lifetime of hurt because it will impact your general relationship genealogy in life.
Whenever you're mature enough to make smart decisions and deal with the consequences if the person you're dating doesn't. I think you need to have a good self image too. If you don't like yourself yet, how can you expect someone else to?
Depends on your personal level of maturity, and on the rules your parents have established for your protection. Some people are mature enough to start dating at 14 or 15, others not until they're older. Trust your parents on this one-they know you best.