sales and use tax return?

[Bryan]

I am an Interior Designer in California and I hold a Re-sellers permit. I purchase home furnishings and decorative items for my clients most of the time. Sometimes I pay tax for the furnishings, sometimes I do not. It depends on where I am and where I purchase from. I need to file a Sales & Use Tax return. I know how to determine my gross sales, but how do I determine my purchases subject to use tax? I purchase everything in california and I either pay tax, or use my re-sellers permit to b exempt from sales tax. I charge my customers sales tax for all the the tangible items I purchase when decorating their job.