What should I do when I fall in love?

This is where you may go wrong in anticipation and expecting success. The love you have is yours that you have developed in you for her. Similarly she too would have developed a feeling which may or may not translate as love

So relax and settle well with in the friendship with her. Don't commit to things and make promises that you may find hard to keep.

Study her behaviour and her thoughts and make her also seek you. Don't act like a stalker by calling her often or messaging her. Never ask what are you doing?
Better to ask what's up!.

Be independent and give her the independence. Keep your calls purposeful .. don't hang on the phone when you run out of content. Instead disconnect and call later so she knows you value your time and hers too.

Short calls for 2-3 minutes is the best.

In short, don't thrust your love on to her and instead let her also develop her love for you

Are you saying you're in love with her already?

If so don't tell her yet, you'll likely scare her. Just play it cool and let things develop naturally, the fact she's had 1 date and is open to another means you're in the game.

Acknowledge she is a free person and whatever she chooses to do (whether or not it involves you) is outside of your control. Once you resign to this you'll be more at peace with whatever outcome floats your way

Just don't be weird.

Just be yourself,