How do film directors (Hollywood and Bollywood) consult actors (Bollywood and Hollywood) for acting?

Alan Chenkin, Likes to watch films
Casting agents will send directors specific types of actors for certain roles. In addition, the Production/finance companies will recommend actors – many of whom will have a dollar amount of funding connected to them being hired for a film (This is because they have a proven “draw / fanbase” and can fill theaters).  When an actor with a loyal fanbase and a $10 million dollar budget increase is suggested to a director, the director is frequently compelled to cast them in a leading role.  If the Director is a Steven Spielberg, or Woody Allen, they will have the final say in casting, and may pressure the production company to use the talent they want – because they have the star power.
How Casting Directors Work – How stuff works
Directors frequently need to work with the actors to get them in the right “frame of mind” to play their role well, and give them motivation and cues that will convince the audience that they are seeing something real.  Directors will also schedule readings and rehearsals prior to any takes, so that the actors are comfortable in their portrayals. Many times directors will have events like picnics and football games in between shoots to build camaraderie between the actors and crew.
Scenes in a movie can be expensive to set up, and anything the director can do (in Bollywood or Hollywood) to get the maximum usable footage is a time and money saving necessity.  In critical scenes, the director may demand many takes, so he has more choices to select the best work.
Your director is motivated to make the best film, and will compel his/her actors to deliver their best.  
 
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Edited and expanded from my answer in Quora.

Do A-list celebrities still need to audition for roles?

They do, but money is often involved.  
A studio may offer specific actors to a producer, based on their known draw. For example, a producer may be told that if you get actor A, we will give you 20 million dollars in production dollars. If you choose Actor B, you may only get 5 million dollars. That is for the A-list stars, who always bring a big audience and large ticket sales just by showing up!
It is up to the producer and director to determine if actor A or B is “right” for the role, so their production will be first class, rather than just a showcase for A-List talent. Keep in mind, even a great actor can’t save a bad script, even if the studios support that decision with production dollars. And a good actor doesn’t want mediocre roles, jsut because they have a strong fanbase at the box office.
A listers have to compete by auditioning when they are up against other a-list actors – especially when the production has a well-known director and a good story to tell.
All the rest of the cast need to audition or have the right age/look/experience/etc. to perform in each role.
From the Web:

The reality is, Actors audition for roles ALL THE TIME.  If your last blockbuster was a big-budget FLOP, you have to work even harder.  There is a long list of former A-list  stars.

No matter what, Enjoy the Show!
 
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Expanded from my answer to this question on Quora.