Some friendships have been faster than others. Deep Conversations are your friend. That interaction does a lot. Try to make them laugh, too.
On the romance angle, I had two Sims raise their romance to about half during a conversation in the park. On their date they maxed it, but the friendship bar is still only about 30%. She moved in with him, friendship will come. I could have proposed but chose to hold off a bit on that one.
I have another Sim couple who can barely get their friendship but and the romance bar is at 10% and slides down a bit every day. They have similar traits, so it's not a clash of good vs evil or anything like that. They just aren't feeling it.
My third Sim couple progressed as you would expect. Friendship first, then romance afterwards.
The key to a good date is having your needs all the way green before heading out the door. Do the interactions the box tells you and the date will get a gold medal.