When water isn't flowing into a toilet, we generally start by shutting off the water supply, then we carefully remove the cap from the top of the fill valve in the tank (ball cock/float valve). Once the cap is removed, turn on the water using a small plastic bowl over the opening to redirect the water down into the tank. If no water comes out the opening with all of the fill valve parts removed, then there is a clog in the line to the fill valve.
The next step is to shut off the water and remove the supply line from the bottom of the toilet, then redirect the supply line into your small bowl and turn the valve back on. If you don't get water out of the supply tube, then you have to shut off the water to the house and remove the valve from the wall, because your blockage is in the inlet to the valve. If there is no blockage at the valve, then you have to start removing sections of pipe back to the meter until you find the blockage.