To ensure the quality of aluminum sheets, first, check for certifications such as ISO or ASTM standards. Inspect the surface for any defects like scratches, dents, or unevenness. The color should be uniform and the edges should be smooth. Request a sample and perform a bend test to check for flexibility and strength. Ensure the thickness is consistent as specified. Look for a reputable supplier with good customer reviews. Lastly, consider the price; if it's too low, it might indicate compromised quality.