How can I adjust my bike chain to ensure smooth and efficient cycling?

To adjust your bike chain for smooth and efficient cycling, first, shift your bike to the smallest chainring and smallest rear cog. Then, loosen the rear wheel axle nuts or quick-release lever to create slack in the chain. Next, adjust the tension by moving the rear wheel back slightly until the chain is taut but not too tight. Finally, tighten the axle nuts or quick-release lever and check that the chain moves smoothly when pedaling.