most celebrities have had their teeth bleached, boob jobs and lip fillers. They have thier own makeup artist, stylist, hairdresser and personal trainer.They also wear(not all) hair extentions aswell. Having lots of money is the answer to the way they look and also they want to look their best as they always in the spotlight. When they are in magazines they are photoshopped to look perfect and flawless.
Have a look at before and after pics of megan fox.

all i can say is just look nice everyday

In most countries, celebs like actors, sports stars, models, etc. get the front hairline treated through hair transplant by FUE method. There is hardly any film star in India who has not got his hairline reconstructed with follicular unit micrografting. In India 3 centers are very popular- Darling Buds at Chandigarh, Pioneer at Bangalore and Excelsior at Kolkata.