Placeholder text for fields in new item form

Hi,

Does anyone know if there is an easy way to show placeholder text in fields of a new item form?

I'd like for the user to see the text (which will tell them what to put in the field) when the form opens, then when they click to fill it in, the text will disappear. I'd rather do this than use tooltips if possible.

I tried entering the text in the "Null display text" field of the control, but I can't see where this text appears.

Thanks for any help,

Mei.