The best way? Just be real about it.
I once slid into someone's DMs by commenting genuinely on something they posted — not a compliment about their looks, but about their actual thought or content. Then a few days later, I messaged them about the same topic, naturally continuing that conversation.
No "hey" with no context. No "you're so beautiful." Just a real, low-pressure opener that gave them something easy to respond to.
The trick is — make it feel like the DM was the obvious next step, not a random move. Reference something real. Keep it short. Don't expect anything back. And if they don't reply? Let it go gracefully. That alone separates you from 90% of people in their inbox.