Avoid being their best friend. You are going to get annoyed too often. They are not good for close friendship.
Instead of trying to change them, improve your social skills, coping logically with the attention-seeking side of them.
Allow them to feel comfortable about who they are. Listen to them, let them know you're listening to them, and you are going to be the center of attention not them.
Playfully tease them about thier behaviour at the right time, at the point of action, then change the subject. It's going to be fun instead of annoyance.
Attention seekers know who they are, they just lack the confidence to assume people are going to notice them just like that. Observe their behaviour, it's fun.
