This advice is probably not for you. Because you're a peerless specimen of well-mannered manhood and also I'm pretty sure only women read my blog. That said.
Relentless sociopaths aside, I think everyone wants to be nice to the woman they're seeing, screwing (sorry, mom) or marrying - especially if they want to see her again, sleep with her again, or not end up at the office with couch cushions imprints on their cheek.
But we're all fragile human creatures. Sometimes our heads are stuffed with other things, sometimes we don't think, sometimes it just didn't occur to us how someone might take something. Therefore.
A Not-At-All-Comprehensive Guide to Being Nice to Her, Because I Believe In Your Potential
1. If you get yourself some water - you know when - offer her some too. Don't just suck it down and leave her to fend for herself. Especially if she's in your house. She's not a camel. Unless she is. Then you have a whole different set of problems, problems I am not equipped to advise you on.
2. If she cares about Valentine's Day or birthdays or Martin Luther King Jr. Day, you get to care about them too. Not because Valentine's Day isn't a corporate shill dressed as an armed toddler, but because it will make her happy.
3. Condoms. I mean, obviously.
4. Talk to her. Let her talk to you if she needs it. Women like talking. Everyone likes to feel heard.
5. But don't talk about your ex. That never goes well. No one likes ghosts. Especially ghosts who are still very much alive and possibly hotter and/or less crazy than she is. (No, I don't speak from experience. Why do you ask?)
6. Make her bacon in the morning. Just saying. (Unless she's vegetarian. Then maybe don't do the bacon thing.)
All this goes for the women too, obviously. Maybe substitute football for Valentine's Day. You don't necessarily have to watch it with him, but you get to be cool about it when he wants to spend six months of the year bowing to the god of intramural testosterone. Because he likes it. Enough said.
Extra Credit Is Given For...
1. Asking her to text you when she gets home so you're sure she's safe.
Yes, we can all take care of ourselves and yes, she managed just fine for 20 or 30 odd years without you, but it's a nice gesture. It tells us that you would care if we got mugged or hit by a bus. We like that in a guy.
Extra Extra Credit For...
2. Driving her home or paying for her cab.
Again, we can get ourselves home and we can pay for our own cabs, but when people do that for me, it just feels really nice. I tend to retain fond memories of that person, that person who cared for my safety and well-being even if he was a little disconcerted when I fell asleep standing up at the bar at eleven p.m. (What? Eleven p.m. is late.)
In Conclusion
It's not always going to work out. But you can leave someone with good memories. Knowing that you behaved the best you could gives you a peace of mind that actually does make a difference in your life. I've acted poorly in situations and have the alarming ability to feel bad about it for years. Seventeen years, to be precise. That's my personal best. High school was rough, man. I'm not wracked with remorse or anything, but if I didn't treat someone the way they deserved to be treated, it eats at me a bit.
So be nice. How else will you get her to turn to you for sex when she breaks up with the next guy?
I'M KIDDING. SORT OF. NOPE, DEFINITELY KIDDING. DON'T WORRY, MOM.
In Real Conclusion
If you're dating her, sleeping with her, or marrying her - just respect her. Show her that you care. That you like her. Even love her. Everyone wants to feel safe and loved. And if she does the same for you? Well, you just might have something there.