The main thing is, don't get frustrated.  I say this as someone who tends to get frustrated. :-)     

The advice in this thread is correct.  The key is to have a white background some distance behind the subject and light that background independently - not perfectly, but bright enough so that all of it - even the dimmer parts - end up saturated, or nearly so, in the photo.  If it's close, you can usually take it the rest of the way by pulling down the white point with a curve adjustment. Center-weighted metering can help you get the subject right while letting the background blow out. Or use a gray card.