There's a lot I’ve picked up tagging fanfic over the years, and honestly the best way to make your queer romance visible is to mix practical tags with vibe-driven ones.
Start with the basics: rating (e.g., 'Teen And Up Audiences', 'Mature', 'Explicit'), appropriate content warnings under Archive Warnings (like 'No Archive Warnings Apply' or more specific ones such as 'Major Character Death' or 'Graphic Depictions Of Violence' if needed), and the relationship tag (e.g., 'M/M', 'F/F', 'M/F/Nonbinary' or 'Polyamory' depending on what you write). After that put the pairing tag—use canonical names or popular ship names so people searching will find you. Add character tags if they’re important to searches.
Then sprinkle in trope and setting tags: 'Slow Burn', 'Hurt/Comfort', 'Fake Dating', 'Enemies To Lovers', 'College AU', 'Soulmates', 'Found Family', 'Fluff', 'Angst', etc. Don’t forget identity tags if relevant—'Trans', 'Nonbinary', 'Bisexual', 'Queerplatonic'—because readers use those. Finally, use freeform tags for mood or meta details like 'Smutty One-Shot', 'Series', 'Content Note: Mentions Of Misogyny'. I usually order warnings first, then rating, then relationship/pairing, then tropes and freeform tags. That structure keeps things tidy and makes your fic easier to discover, and that little bit of tag hygiene makes me way more likely to click and read.