It's very simple. When you think the time is right to kiss her - which should be as you are leaving, stand about a foot away and look into her eyes. Smile, and incline your head slowly towards hers. She will either respond and move as though ready to be kissed, in which case you kiss her gently and slip your arms around her. Let her dictate how passionate the kiss is, and respond accordingly.
If she doesn't want to be kissed, she will incline her head away, in which case you gently kiss her on the cheek, and say goodnight. You will know from her body language if she is comfortable with this next time you meet - if so, make it a little ritual, if not, then do nothing. If in the future she wants to move things on a stage, she will give you the signals that it's OK to kiss her - mainly by looking like she'd like you to!
Either way - you either know she is interested, and if not, you both emerge with your dignity - and more importantly your friendship - intact.