Similar to the previous question – you don’t. But there are things to consider.
The first thing to look at is whether you have the same values and beliefs. Then, make sure there's a strong mutual connection, a feeling of compatibility, and chemistry.
You’ll also want to look at whether you’re both happy with where you are. And lastly, consider how the relationship would be for your future.
If everything fits into the right places, the chances are, he/she is the one!