This post explains how to remove a bicycle tyre and tube, with step-by-step instructions. How to start:
After that follow the procedure:
1. Remove valve cap and valve holding screw (if present)
2. Completely deflate the tyre
For dunlop valves, unscrew the valve holding screw and take the valve core out. For presta, just unscrew the valve safety, same as when inflating the tyre, then press the valve down to deflate. For schrader (auto) valves, either press on the valve core with a sharp object, or remove the valve core with an appropriate tool.
3. Unsticking tyre from the bead
4. Removing tyre off the rim
Tool is put beneath the tyre, carefully not to pinch the tube, then it is pushed downwards and hooked onto the nearest spoke (tools have special hooks on the low side).
Best with three tyre removing levers, tyre is taken off the rim.
5. Removing tube
In the end, tube needs to be removed. Start from the side opposite to the valve and just pull the tube out.
Then pull the valve out, moving tyre aside. That frees the tube completely.
When one side of the tyre is moved off the rim and the tube is taken all the way out, tyre can easily be pulled all the way off the rim.