Show a radio button or checkbox as checked?

I have a bit of a newbie question here.

I have two radio buttons that are grouped (yes and no values). When I
come to edit a record, how do I get the radio button to be checked?

I found a helper method on another site, but it doesn't appear to be
working. I can't seem to get the checked state to show for either a
radio button or checkbox?

Can someone help me out?

Thanks,
Sarah

Newbie error. Make sure your object is the right one.

Sorry for the useless post.

- Sarah