Important Considerations:
* Shop Manual: A factory shop manual is absolutely crucial for this job. It will provide the correct valve lash specifications (clearance), the firing order, and detailed procedures. Attempting this without it is strongly discouraged.
* Tools: You'll need the correct feeler gauges, a torque wrench, and possibly special valve adjustment tools depending on your engine design.
* Safety: Working on your vehicle's engine involves potential hazards. Always disconnect the negative battery terminal before starting any work. Be mindful of hot components and use appropriate safety precautions.
Do not guess or follow general advice found online for this; always use your vehicle's specific shop manual. Incorrect valve adjustment can severely damage your engine.