GMing romance plots is dangerous. Just look at reddit or watch any YT videos about awkward D&D table issues. There's so much that can go WRONG - yet it's so EASY to get right. I run romance interests and plots for my players each week.
Here's how…
Session 0 -
You need to express expectations, lines, veils, and safety tools. You absolutely need an X (stop) and/or N (veil) card in play if you're going to allow romance or intimate contact. People have a right to change their minds mid-game - allow them the space to.
Start with your lines/veils and rules. I don't allow myself to initiate with players as an NPC without consent. I'm in a position of power as GM, so it might be seen as something that "has to happen" in the context of a plot. That's not true. So I eliminate the threat of it.
Clarity -
In that same vein, if a player initiates with me, I consider that to be temporary consent. My NPC will flirt back. If I feel uncertain, I will ask directly: "Is your PC flirting?" Sometimes the player will say "Oh! No." That's okay. People communicate differently.
As a GM you need to be ready for that uncomfortable clarification. People at your table sometimes won't feel comfortable expressing themselves unless prompted directly, in private or in public. Use your discretion for this.
Temp Consent -
If I have temporary consent, (they flirted with an NPC) I will check-in with the player post-session. "How was that? Did you have fun with this? Is this something you want to continue?" Again: consent is not something you gain once and have forever.
Ask -
If I ever feel as though I want to run a romance plot that involves their PC, I will ASK FOR PERMISSION explicitly to the player in a private message. This is to eliminate: Peer pressure, awkwardness, and potential embarrassment. If they don't want it? I don't either.
Planning Romance -
If I'm wanting to do a thing for story reasons I will plan a 4 plot point story arc.
Initial awkward romance
Serious confession
Commitment/Conflict
Resolution
I check in privately at each stage. Usually after every session with romance, even.
These can be fit in nicely during downtime usually or in conjunction with a major plot. These are "b plots" that you find in many series dramas. They're meant to incite direct interest for short periods of time, but not be the main story. They can also humanize former antagonists.
Value -
What can romance plots do for your table? Well, for some players they are an important facet to what it is to be human. If you do this carefully and intentionally, you can really invest your players.
Apologize -
You're going to make mistakes. Be ready to admit a mistake and listen to your players if they express discomfort. Your romance script is not as important as the safety of your players.
Modify Memory -
You might need to drop a plot. Someone could be having a rough time IRL. The romance could be stressful and not fun anymore. For any reason if a player wants to - I allow a player to X out of a relationship, vaporizing it. (As though it never existed.) It’s easier for me to cut out the problem than to lose a great player.
What if you want more than this article can tell you? You’re in luck. We’re launching How To GM Romance soon! Check it out.
This seems to be something in the ether. Kismet Rose just finished a whole series focused on things like this.
Another great set of advice. I discuss romance during Ses 0, but bringing it up later is also important. I esp liked the advice about straight up asking "I will ask directly: 'Is your PC flirting?'" That level of clarity can go a long way to avoiding anything that might build up later