Just curious, if I'm interested in doing an adaptation, say for example, Roald Dahl's Going Solo, when I contact the publishing house what rights exactly do I need to ask for? And, on that note, should I purchase the rights before actually putting anything onto the page? Thanks guys
You would need to acquire the movie rights -- to be precise -- you'd need to acquire domestic and international movie rights.
But to be even more precise, what you'd really need to do if you were really interested in persuing this is to get yourself an entertainment attorney (a regular attorney would not do) to negotiate this deal.
As a writer, you can't do this. The act of "acquiring rights" makes you a producer. It means that you've become the owner of a property -- the owner of the underlying rights to the material.
Regarding "whether you should purchase the rights before putting anything on the page" -- this is the same as asking "should I buy the car before customizing it" -- generally the owner the car would greatly appreciate it if you were to buy their car before making your own alterations -- especially since the property in question might very well have have had the rights sold to somebody else before you ever even came along.
Depending on the cost (and don't think for a minute that they'd let you have it for free because they like you) you might be able to option it -- that is, pay a small percentage for a certain length of time during which you can write your script and try to sell it.
But if you can't sell it and the option expires, you're out of luck. It goes back to them and your script becomes forever unsellable.
On the other hand, you can spend a lot of money, buy it outright, write your script. Nobody's interested. End of story. You own it. Nobody wants it, you've spent a lot of money on something that will never sell. Bad deal.
Either way, you'll spend a lot of money on a lawyer and probably significant money on the underlying property.
You might save some money on the lawyer by investigating if your state has a "volunteer Counsel for the Arts" -- most states have them - in which lawyers provide free or inexpensive legal services for members of the arts community.
If so, you might be able to get an attorney through them to advise you.
NMS