How can i tickle a girl's armpits?

Tickling someone's armpits should always be approached with consent and respect for their boundaries. If you have a playful relationship and know she's comfortable with being tickled, you can gently touch or brush your fingers against her armpits while keeping the atmosphere light and fun. Always pay attention to her reactions and stop if she seems uncomfortable. Communication is key to ensuring that the experience is enjoyable for both of you.