Adding custom text fields to RT

We are using RT to manage a queue of customer support related issues,
There are still a couple of requirements that we could not meet using the RT web
interface for configurations…
(So I am hoping that now the fun can begin, a little bit of mason is no problem
so any pointers to examples will be very welcome)
Is there any documentation on how to add a custom field that is not a keyword to
a specific queue ?
Can I add a free text field into the keyword selections?
Is there a comfortable way to add a date selection keyword?