Usually it's Christians who ask me this question, and I keep it very simple:
"I believe that [1] God is sovereign, and [2] Jesus Christ is the Saviour of the world. Everything I believe can be summed up in those two things."
Of course, most of the time they don't realize how different that is from what
they believe. They
think they believe the same thing. "Oh yeah, I believe that too. That's cool."
If they want me to get more specific, or if they are curious about my "heretical" beliefs, I start with the Seven Scriptures from the Foundational Truths study [still my favorite study that Ray has ever done
]:
[1] 1 John 4:14 And we have seen and do testify that the Father sent the Son to be the Savior of the world.
[2] 1 Tim 2:3-6 For this is ideal and welcome in the sight of our Saviour, God, Who wills that all mankind be saved and come into a realization of the truth. For there is one God, and one mediator between God and men, the man Christ Jesus; Who gave Himself a ransom for all to be testified in due time.
[3] 1 Tim 4:10 We trust in the living God, who is the Saviour of all men, especially of those who believe.
[4] 2 Peter 3:9 The Lord is not willing that any should perish, but that all should come to repentance.
[5] Isa 46:10 Declaring the end from the beginning, and from ancient times the things that are not yet done, saying, My counsel shall stand, and I will do all My pleasure.
[6] 1 John 4:8 God is love.
[7] 1 Cor 13:8 Love NEVER FAILS.
Another good one to add to the list is Phillipians 2:13: "for God it is who is working in you both to will and to work for His good pleasure." [YLT]