One study found it takes around 50 hours together to turn an acquaintance into a casual friend. Keep showing up.

Friendship is mostly a function of hours spent together, and the number required is larger than people expect. That is why somebody you like at work can stay an acquaintance for a year: you have had thirty pleasant five minute conversations and almost no actual time. Nothing is wrong with either of you, there just has not been enough of it yet.

Pick one person you would like as a friend and create a block of time rather than more passing chats. A walk, a lift, a long shift, something weekly. Hours do the work that charm gets credited for.