At the risk of sounding stodgy, a few words about manners: Use them – always and as naturally as possible. Good composure at the table indicates good composure elsewhere. A few key principles: offer her the more comfortable seating, and the better view. Invite her to taste the wine (before or after you do) when the server presents it. Don’t get drunk, or noticeably so.
As for dinner, offer her a bite of your dish, but don’t eat off her plate unless enthusiastically invited. Say “excuse me” before standing to head to the restroom. And yes, be respectful to the service staff. If something is wrong with the food, address the problem immediately and politely. (Coarse confrontation is hard to digest.) Dessert? It doesn’t matter if you’ve saved room or not: she wants some.
If you have her to your place for a meal, cordiality is even more critical. She’s on foreign territory, and a dose of consideration will put her at ease. Before she arrives, eliminate any potential distractions: clean your living quarters, empty the dishwasher, set the table, and put on that playlist (long enough to last the evening).
When she arrives, have a drink and perhaps a snack ready to keep her occupied while you finish cooking. (You’ve taken careful mental notes on previous dates, so you’ll know what she likes to drink.) Better yet, stop what you’re doing and have a drink with her; this will show that she’s more important than the dinner and that the kitchen is under control. She’ll probably ask, “ What can I do to help?” Your first answer is “Nothing. Have a drink and relax.” If she seems truly eager to assist, let her pitch in, but pick a task that’s not mundane or intimidating. (Chopping parsley = fun; scaling fish = punishment.) Otherwise, keep her entertained by offering her the occasional taste.