Honestly, the best approach to take is a listening and seeking to understand approach.
The abortion issue can get so polarized and debate and arguments are rarely going to change anyone’s mind.
What you want to aim for is to be the kind of safe person that someone in a situation where abortion might enter the picture as an option will be drawn to confide in you. At that point you can express your support and you can also recommend resources that could help. People facing a crisis pregnancy need love and support more than anything, and often it is the presence of that support which helps people to on their own make the choice to carry the baby to term and then make good parenting decisions for that child. And should that happen, this friend will need your support for the long haul. Also, your support needs to remain no matter what the parent chooses. That’s not to say you condone abortion, only that one who has that experience will need love and support.
As far as articulating your views, if you’ve listened to others at least some of them might be open to what you have to share. Focus your conversations on the subject to people who are genuinely interested in learning from you. In that case you won’t need to say things just right or have polished arguments. Just share from your heart.
You might also consider getting involved with reputable charities and ministries that support new mothers and their babies as well as parents raising at risk children. You can also contribute financially. In this way, you are taking positive compassionate action that can be truly lifesaving for others.