FOLLOW DIRECTOS AND ACTORS IN IMDB

I feel the same way!
The same was asked three years ago thou, nothing actually changed...
https://getsatisfaction.com/imdb/topics/follow_items_on_imdb

I was about to add the same idea as a post till I saw yours. It would be a great function and to be frunk, I don't even know why this is not yet implemented. 

Check an actor/director or even a writer, add him to your follow-up list (in a similar manner you add a movie to your watchlist) and be immediately notified about each production/movie etc he is acting to or he has directed. Simple as that!