1
Get her alone. This is probably the most important thing you can do to make your kiss romantic. If you try to kiss a girl in front of your friends, she'll think you're trying to show her off as a trophy. Instead, make it seem like an intimate and special moment by making sure you're alone with her. Pull her away from the pack with these tactics:
Tangle your hands up in hers, pull away, and look into her eyes.
If you're with a group, ask her to hang back with you for a minute.
Even when you are surrounded by people at least try to touch her, like hands, shoulder etc, confidently to sub-communicate your intentions.
In school you can ask her to go to your locker with you or a walk around the school. It's very romantic in the summer or in autumn.
Ask if you can walk her home, whether it's from school, work, or a party.
Or, if all else fails, ask her out on a date if you want! That way you're guaranteed alone time.
2
Set the mood. Make sure the atmosphere around you is romantic, and half of the hard work is done! Going through the effort to set up an enchanting scene communicates how you feel, as well as making it easier for her to see you in a flattering way. Here's how to do it:
Find a softly-lit place. It's probably possible to come off as charming in broad daylight, but it's not easy. Instead, find a setting that has forgiving lighting that conveys a sense of romance. Try these ideas:
Sunsets are considered universally romantic, especially if you have a good viewing point
If it's a full moon, you could rely on the moonlight — you should still be able to see after your eyes adjust.
If it's a rainy day, find shelter under a porch or in a car. The small amount of light filtering through the rain should be shimmery and soft.
If you're camping or at a bonfire, make use of the flickering firelight! To recreate the look indoors, you can light a few candles.