A Jehovah's witness I know, when I had asked, "How does a person know they are a Christian?" answered something like, "You know you are a Christian when you are following closely in the footsteps of Jesus." Of course, in his mind, a lot more goes along with what he would define as a footstep follower of Jesus. Even so, I think that is the best answer he could have given.
2Cor 13:5-9 KJV
5 Examine yourselves, whether ye be in the faith; prove your own selves. Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates?
6 But I trust that ye shall know that we are not reprobates.
7 ¶ Now I pray to God that ye do no evil; not that we should appear approved, but that ye should do that which is honest, though we be as reprobates.
8 For we can do nothing against the truth, but for the truth.
9 For we are glad, when we are weak, and ye are strong: and this also we wish, even your perfection.
2Cor 13:5-9 BBE
5 Make a test of yourselves, if you are in the faith; make certain of yourselves. Or are you not conscious in yourselves that Jesus Christ is in you, if you are truly Christ’s?
6 But it is my hope that you will have no doubt that we are truly Christ’s.
7 ¶ Now our prayer to God is that you may do no evil; not in order that it may be put to our credit, but so that you may do what is right, whatever we may seem.
8 Because we are able to do nothing against what is true, but only for it.
9 For we are glad when we are feeble and you are strong: and this is our prayer, even that you may be made complete.
It looks to me that being a Christian involves a personal examination, or testing, marked by doing what is right, that is, doing no evil.
Ro 13:8 Be in debt for nothing, but to have love for one another: for he who has love for his neighbour has kept all the law.
Now no one is pefect, and who loves all the time, every moment of the day? Most days I don't feel right, perhaps a part of my illness, I do not feel like a Christian, I'm not so sure I'd say I am one, but here are a couple of verses to ponder from the bible that I found.