There are some movies where you should just choose to leave your head behind and see only the movie. This movie, Hum Tum aur Ghost, is somewhat similar.
The plot is fairly simple, you have Arshad Warsi, playing Armaan, a fashion photographer who's a heavy drinker, assisted by a gorgeous Sandhya Mridul, playing Mini, in love with Dia Mirza, playing Ghehna, who's supposed to be the editor of Cosmopolitan (and is not seen under pressure, is not hyper fashion conscious, or busy at all!). That said, you have an entire entourage of "ghosts" who are following Armaan, because he has the "gift" to see, and hear them.
Similar to the Sixth Sense, each of them have died having something unfinished and need help from him to complete that deed so that they can move on to heaven...
It's interspersed with some comic dialogues, and some great acting esp. by Boman Irani, and Sandhya Mridul. Arshad Warsi fails to evoke the right sentiment of pity, warmth, and affection in you, Dia Mirza really can't act. She just acts hyper, and that's really got no depth. I think she gave her best performance in RHTDM.
The story in the end makes up for the shortcomings in between, the point is, it could've been so much better! Even the comedy part of it could've been more humourous had the screenplay and the script writers paid more attention to detail.
I mean seriously, Dia Mirza being the editor of Cosmopolitan magazine could've delved a little more into her character, you can't just wear a slinky gold dress and be the editor of a fashion magazine, you have to be crazy, busy, neurotic, she was behaving as though she was the daughter of the editor (who also owned the magazine), and had absolutely nothing to do in office but while away time whispering sweet nothings over the phone!
All this said, it's still a better movie for a one-time watch than most of the other movies around!