Any advice? I have two specific couples in mind, one homo one hetero and it's a slow burn for both but I feel like I haven't done a great job setting it up. What are some ways to make it clear to the reader what's going on?
You can have one of the characters catch the other one staring at them. Staring is usually a dead give away to a budding romance XD. Maybe person A sees person B do something rather cute, like flipping their hair, and person A might call them adorable or tease them. They can even just admit to themselves that they found it attractive.
Teasing is a great way to build sexual tension. Especially is it's targeted at a height difference.
If person A gets put in danger it will give you the perfect chance to show Person B being protective and showing their true feelings.
Hope this helped! Let me know if you have more questions.
Oh boy, oh boy. There are soooo many ways to show sexual tension. (I'm gonna mention some stuff that's already been said because they're good points!)
Think about your plot. How do they meet? (It's a memorable moment for both your characters and your readers. Do they meet cute? Do they initially hate each other? Have fun with it!). How do they interact with each other after that? Are they forced into situations together? Do they keep bumping into one another? Do they acknowledge their feelings for each other? Is one oblivious? Do other characters know what's up? Do they want the same things?
Add some conflict! Think about why these characters should be together, then think about all the things that could stop these characters from being together. We all want things we can't have. Obstacles. Add. Tension.
It also depends on the dynamic your characters have. Opposites attract is pretty fun to work with when building sexual tension. Is one of them shy while the other one is confident? Is one of them pessimistic while the other is optimistic? Is one the hero while the other is the villain? Your readers could make a link between them simply because they don't share the same qualities. Figuring out what these characters would have in common would then catch the reader's attention.
Have them support one another through difficult times. When character A is in danger, have character B there to save them. Or have Character A hit rock bottom and character B there to pick them up. Show that these characters, despite being beaten up by whatever your plot is, still manage share light-hearted moments with one another.
Use the senses to describe things your characters notice about each other. It's more intimate. Maybe one of them wears a memorable cologne. Maybe one of them has a deep voice. What about the love interest is distracting to your character? Also, your character is (probably) going to want the love interest to notice them too. So maybe they act a bit different when they're around. Perhaps they start trying to do things to impress them. Rivals are a fun dynamic to play around with there.
Don't worry about your readers not catching on. If you want these characters to be together, your readers will know. Majority of readers will already have their little detective caps on trying to work out what relationships (if any) are going to happen. You're just sprinkling in little clues to help them out along the way, there's no need to spell anything out straight away. Just imply. Even if they don't initially catch on that's fine. You're building the story up for the reader to show why these characters would care about each other.
Here's some other examples of smallish clues that you can use to help out readers:
I'm not an expert or anything but i hope that helped! If not, you could always draw inspiration from your favourite tv shows/movies/books. Find which relationships are your favourite to watch or read and make a list about why you like them. At the end of the day, you're the writer, so write the things that you want to see out in the world!
@Fairlyodd That was so much better than my measly paragraph XD
@SpaceCat446 I spend too much time torturing my characters with sexual tension haha. Besides I mentioned a lot of the stuff that you'd already said! xD
It's also important to note that there's different types of sexual tension. There's the more repressed pining type with long glances and awkward hand grazes; there's belligerent sexual tension with snark, banter, and conflicting personalities; the dark "will they/won't they" sexual tension of enemies that makes you and the characters question the morality of the ship; and probably more variants as well.