Let’s start with some previous posts on the subject.
- Adding Subplots to a Novel
- Weaving Subplots into a Novel
- 7 Ways to Add Subplots to Your Novel
- Crafting a Successful Romance Subplot
- How to Improve your Writing: Subplots and Subtext
- Understanding the Role of Subplots
- How to Use Subtext in your Writing
- The Secret Life of Subtext
- How to Use Subtext
Think about the ways your characters would show they like someone/have interest in them. Do they blush? Do they get really quiet or do they laugh too much. Any nervous ticks? You can add subtle things to grow a relationship without hitting the reader over the head with it.