>>The question is - how can I add them to my user controls?
>
>well, drag it from the Toolbox into your user control
>

Thanks a lot, I was thinking it would not work without having Script Manager in the user control thus I didn't even try.

>> Where should I specify the Script manager?
>
>the script manager has to be in the webpage, in wich you want to use your user control.
>
>You need only one script manager per page and its recommended, that the script manager is the first control in that page.
>
>If your using a masterpage, and your masterpage already contains a script manager, then you should use the script manager proxy control inside the content part.

We're using MasterPage, but we didn't put Script Manager there. It is used in page by page basis, which is not really good way, IMO.