The answer to this question is to always be honest. Always, If the question asks if you were ever convicted of a felony and you have been convicted of a felony, then the proper answer to put down is "yes." It doesn't matter if you were convicted when you were a juvenile, if it has been expunged from your record, or if it occured 30 years ago. If the question asks if you were ever convicted, then you have to check yes if you want to be honest. And you should never lie on any application because it can only come back to haunt you.
Most employers are probably going to consider the nature of the crime and how long ago it occured. If a significant amount of time has passed, you can demonstrate rehabilitation or a steady streak of clean living since, or if it occured when you were a minor and now you are an adult, then it probably isn't going to have as much of a negative impact as if it had been more recent or if they discovered you lied about it. Employers appreciate honesty and most will probably be willing to overlook a juvenile indiscretion as long as you are upfront about it.
So just be honest with your potential employers and point out that you have had nothing on your record since. Good luck!
I tend to disagree somewhat with the first answer. A juvenile adjudication is not the same as an adult felony conviction, and I do not think that it is required that you disclose it on an employment application.
However, with that being said, you should be aware that the juvenile felony adjudication will likely show up on a background check, particularly if you are applying for a government or county position.
You may want to consider disclosing the juvenile adjudication, but giving potential employers a detailed explanation about how this incident happened several years ago, while you were very young, and that you have gone on to become a successful adult.
I think that you are going to have more difficulties becoming employed if you do not distinguish the fact that this was a juvenile felony adjudication, compared with an adult felony conviction. Make sure that your potential employers are aware of that fact.
Good luck with your employment search!