I simply named "pinball" and a dollar amount (rider policy), it is still part of my personal property coverage. But there are limitations on many things. Tools and jewelry are another. That said my insurance company only covered $2500 for tools by default. Most people will get caught by that. I add $7500 for a total of $10k on tools for a negligible amount. Swamp fire is right, reading the policy is how I determined my limits.
Another factor in determining the additional fee for the rider is deductible. I opt for a fairly large deductible (self insure) and insurance is not that bad.
I am different than Mr Bally in that I don't believe in minimal insurance (legally required). I believe in covering maximal loss with a high deductible. If someone slips and falls and sues for $500k I want to be covered to the max, not the minimum. However the cost of a minimal policy with a small deductible is just as much as a large policy with a large deductible. But to me the real risk is big bucks, not a hit for $5000 or 10k (granted it would stink, but you can recover. but I am willing to incur a reasonable risk). It's the big life changing events, house burns down, someone sues, you rear end a brand new escalade......major life impact that you need insurance for. You want to insure for WHAT YOU CANNOT AFFORD TO LOSE!