1. Use Sharepoint Designer, open your site and expand the directory of your list
2. Find the form where you wish to hide one or more fields (I obviously really feel strongly about changing EditForm.aspx and NewForm.aspx) and open it in code view.
3. Locate the placeholder for the main content:
<asp:Content ContentPlaceHolderId=”PlaceHolderMain” runat=”server”>
and insert the following script immediately after:
Now you can swap “SomeFieldName” to the name of one of your fields and it will disappear. Add as many fields as you wish (each field requires both the findacontrol() invocation and setting the style).