You can blowdry you hair upside down for extra volume but ultimately the secret is in the products that you use. Using professional products to create volume is essential. Your "off the shelf" product’s molecules are too big and only sit on the surface of the hair, thus causing build up and weighing the hair down unnecessarily. Big velcro rollers also work well. Rough dry your hair until it is dry and then pop the rollers in for 30 minutes. You can spray hairspray on your hair while the rollers are in. I would recommend using REDKEN’s Body Full Shampoo R210) and Conditioner (R242). This has an Anti Gravity Complex which lifts the roots, but still moisturises the ends without weighing the hair down. REDKEN Rootful (R260) styling aid. You spray this onto your root area before blowdrying and this gives you the ultimate volume. MATRIX Amplify Shampoo (R105), Conditioner (R125) and Wonder Boost Root lift Spray (R150) are also a great alternative to use.
These are available at professional salons.
MIRRORS hair lab