Look for someone who loves Jesus and has the character to prove it. Chemistry matters, but feelings fade. Character lasts.
Who you marry is probably the biggest and most important decision you will make in your life. If you're asking this question, you're already ahead. A lot of people never stop to ask it until they're in too deep. God cares about this decision even more than you do.
What the Bible says
1. Start with faith. "Do not be unequally yoked with unbelievers" (2 Corinthians 6:14 ESV). Paul says a widow is free to marry whoever she wishes, "only in the Lord" (1 Corinthians 7:39 ESV). If you don't share a faith, you don't share a foundation.
2. Look at character, not just charm. "Charm is deceitful, and beauty is vain, but a woman who fears the Lord is to be praised" (Proverbs 31:30 ESV). Jesus said, "You will recognize them by their fruits" (Matthew 7:16 ESV), and the fruit of the Spirit makes a pretty good checklist: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control (Galatians 5:22–23). You're dating who they are, not the potential they have. Everyone has potential. Their potential isn't a green light; their character is. When someone shows you who they really are, believe them. And you will not change them. The best indicator of someone's future behavior is their previous behavior.
You can see this in the story of Ruth. Boaz didn't notice her because of a great first impression. He noticed her character: how she worked, and how she'd cared for her mother-in-law (Ruth 2:11–12).
3. Guard your heart while you find out. "Guard your heart above all else, for it determines the course of your life" (Proverbs 4:23 NLT). Song of Songs repeats it three times: "Do not stir up or awaken love until it pleases" (Song of Solomon 2:7 ESV). Slow down long enough to actually see them.
4. Listen to the people who love you. "The way of a fool is right in his own eyes, but a wise man listens to advice" (Proverbs 12:15 ESV). Those who love you most should be listened to the loudest.
Throw out the wish list. A lot of people have a husband list or a wife list. Has to be 6'3". She has to be a redhead. She absolutely cannot be a redhead. Must be killer at Call of Duty. Can't be a flat-earther. Replace your wish list with a question list:
Are they a growing believer? Is the Bible an authority in their life? Do they go to church even when you're not there?
How are they with money? How much debt do they have? Do they keep a job?
What are their sin struggles, and are you OK walking that out with them?
Are they selfless, or do they always need to be right?
How's their emotional maturity? How do they handle conflict and disappointment?
Are they honest? Do they hide things?
How is their purity? Are they addicted to pornography?
What's their family like? Would you trust them to raise your kids?
You might be thinking…
"But nobody's perfect." True. I'm all for grace, forgiveness and allowing space for people to change. But if you find yourself making excuses for their behavior all the time, that's a red flag.
"They're not a Christian, but they're a really good person." I believe you. But "good" isn't the standard God gave us; "in the Lord" is. Dating someone and hoping they'll come to faith puts you in the role God never asked you to play.
"Doesn't attraction matter?" Of course it does. There's a whole book of the Bible about it. But the chemistry you feel can't compensate for the character they have.
Next step
Answer the question list honestly about the person you're dating. Then hand it to someone who loves you and knows them, and ask what they see.
Related questions
Scripture: 2 Corinthians 6:14; 1 Corinthians 7:39; Proverbs 31:30; Matthew 7:16–20; Galatians 5:22–23; Ruth 2:11–12; Proverbs 4:23; Song of Solomon 2:7; Proverbs 12:15