Per Rick's advice, from Hlavni Nadrazi we took an AAA taxi, across the street from the Hotel Chopin. It costs us 140 CZK to Hotel Metamorphis. Five days later, we told the Metamorphis clerk to call us a cab and that we wanted wanted to go to Hlavni Nadrazi. The clerk handed my husband a printout which said that the trip would cost us 300 CZK, fixed rate.
We went to the i (Czech Touist Information) on the Town Square and asked where the nearest Fair Place taxi stand was since Rick Steves had said we would get a better chance of getting an honest cabbie. We were told there was a stand about a block and a half away from the Tourist Info off and that the ride would cost about 140 CZK. The clerk suggested we walk to the train station if we didn't have too much luggage and that it would take 7 minutes. We walked to the Fair Place stand to check things out. I asked one of the AAA cab drivers how much a trip to the main train station would cost, and he said 240 CZK plus tip. I then tried to locate the name of the Fair Place location on the informational sign; this would tell me how much it would cost to get to the main train station. I couldn't locate the name of the Fair Place location so asked the cab driver what it was called. He said it wasn't on the list and that the list was wrong.
We returned to Tourist Information and told the clerk who was quite surprised and repeated that the cost should be 140 CZK; he also asked "tip for what?" He said the stop was right behind St. Nicholas Church and that might be the name to look for on the informational poster.
My husband googled the distance; the estimated time was 17 minutes to walk from Metamorphis, but we estimated for us about 25 minutes. For that reason, we will probably still try to get a cab at the Fair Place station, tell the cabbie how much our first trip cost, remind him to set the meter at #1 tariff, and hope for the best.