Where to place the JavaSript in SharePoint Foundation 2010's list form?

Hi Guys,

We are new to SharePoint 2010 so we just wanted to ask these questions.

1. We are using SharePoint Designer 2010 for editing a list form (NewForm, EditForm and DispForm) in SharePoint Foundation 2010. From the block of codes behind a form, where should we exactly place the JavaScript or the JavaScript function (maybe a place before or after a certain tag)?
2. I heard we can also insert the script on a Content Editor Web Part. Will it be the same if we are going to place it on the code behind the form?
3. How to properly make a function call in the code behind the form? Let say on a button click. Can you give an example code?
4. Also, is it possible make a function call by creating a script in notepad, saving it in the Shared Document library and referencing the source of the script in the code that you will place behind the form or in the Content Editor Web Part?

Thank You,

Arnel