Word factory: One of the most important and challenging aspects of a script is its length. Everything I've ever written (except for Dr Babasaheb Ambedkar) has been under 120 pages – the norm for international screenplays.

It's like a haiku or sonnet. Whatever needs to be said must be said within these parameters. Rule of thumb – one page translates into one minute of screen time. So, a 120-page script gives you a film with a running time of 120 minutes. This gets whittled down further, to about 90 pages when it is time for the shooting script.

Show, don't tell: Try to narrate the story in images rather than lengthy dialogue. For example, a scene from Salaam Bombay – where we needed to convey that eight-year-old Manju is jealous of the older Solasaal, who she thinks has usurped her friend Chaipau's affection.

Instead of expressing her jealousy in dialogue, this is how it was written: Chaipau asks Manju to deliver a packet of biscuits to Solasaal. Manju does so, but outside Solasaal's room, instead of giving her the biscuits she gobbles up the entire packet.

Mira's direction to Hansa, who played Manju was to eat the biscuits imagining that she was eating up Solasaal. She did it perfectly. The audience got it.

The plot thickens: A good script is a combination of a strong story (plot) and interesting characters. It's like a tree – where the plot forms the trunk and the characters are the branches and leaves. Without the spine, the tree can't stand and devoid of branches, the tree would be ugly and uninteresting.

Free flow: You can either map out the entire story in an outline form and then follow the outline as you write, or you can let the story flow as you write it. (Sometimes directors/producers/financiers insist on an initial outline).

I find following a map boring. I also believe it cuts you off from the interesting possibilities and surprises that always emerge in the actual writing.

I like to have a general idea of the story in my head when I begin. Then I outline small segments at a time, a mini-map that changes as the writing progresses.

Money: In India, I am told that compensation for scripts varies depending on whether you write the story, screenplay, dialogues – since each screenplay is fragmented into different jobs done by different writers.

I've heard that payments can vary from Rs 1 lakh to Rs 25 lakh. Writers in India can and should register their scripts with the Film Writers' Association.

How to break in: Meet directors with your ideas/scripts and hope that one of them 'discovers' you. Or go the film school route. In America and the UK, one person writes everything – story, dialogues – called the screenplay.

In the US, one can and should register scripts with the Writers' Guild of America (WGA). The registration is open to all, regardless of nationality, and one can do it online from India too.

Adaptations: I believe in respecting the original, re-imagining it for a different medium. I have a bookmark that says 'Never judge a book by its film'. Unfortunately, many times this is true.

Adapting a novel is a paradox. You have to preserve its richness and density while simultaneously cutting it down to a fraction of its original length. I've been fortunate to have adapted some brilliant books, which makes my job easier as well as harder.
Easier, as the story, the characters, the dialogue are already all there. Harder as there's such an embarrassment of riches – what to keep, what to cut?

Page one: Over the past 19 years, I've written more than 19 scripts and facing the first blank page never gets easier. It's the hardest part of writing for me.

However, if you keep at it, the car does accelerate and soon hopefully you'll be flying down the Mumbai's Pune Expressway. It's important not to give up.

Rewrites: All the scripts I've written that have become films, have gone into seven drafts each. Sometimes, scriptwriting is endless rewriting. Each time you have to summon up the enthusiasm, even though you are reworking the same repeatedly.

If you're bored, it will show on the page. If you are blessed, the script will get made.