When they seek attention to a point that is annoying it's better to ignore them. If they're family members of friends, a subltle talk on the subject could work or not. I try it sometimes, I try not to tell one they're seeking attention I just go straight to the behavior, pointing what I think is wrong or not.
Most people want some attention at some times. But I guess you are talking about constant attention seekers. I guess sometimes I ignore them and sometimes I try to help them figure out why they are doing it and how to stop because sometimes there is a deeper problem underlying the attention seeking.
I have given them my attention before and they just ignore me. I have came to realize they don't want your attention; they want attention from someone "better" than you. I have stopped giving them my attention because they don't deserve it.