How do you take correct timing of 1.7TD Opel Astra?

To set the correct timing on a 1.7 TD Opel Astra, first ensure the engine is at top dead center (TDC) on the compression stroke for cylinder one. Align the timing marks on the crankshaft and camshaft gears, ensuring the timing belt is properly tensioned. Double-check that the timing belt is correctly routed and that all timing marks are still aligned after tensioning. Finally, rotate the engine manually to confirm there are no obstructions before starting the engine.