Change SSRS Parameters or Form Defaults 10.0.700.4

I have created a new report style for the Sales Gross Margin report that gives a simple one line summary for each product group. In order for it to run properly, it needs to be sorted by product group and have the adjusted cost box checked.

I have done some customizations but haven’t dealt with changing defaults. I found some online resources that might get me there if that is the best route.

What is the best way to either customize the defaults in the report form or override the parameters within the SSRS report?