Instructions
Go to eBay. Many people sell Mattel dolls from the 1960s for good prices on eBay. When shopping on eBay, make sure you look at pictures, feel free to ask the seller any questions and note any damages to the dolls before buying them.
Contact antique stores in your area. Many antique stores sell dolls from the 1960s. See if you can get onto mailing lists or have the owners of antique stores contact you if they come into some Mattel dolls for sale.
Learn what to look for in dolls from the 1960s. The hair and clothes should be original, the eyes should be clear and open and close (if they did that originally) and the body should have no discolorations. Read books and articles online to find out more about Mattel dolls from the 1960s.
Attend doll shows. Doll shows are great places to network with other collectors, speak to sellers of Mattel dolls, see in person many different kinds of dolls and even purchase some dolls for your collection at good prices.
Shop at garage sales, especially if you like fixing up dolls. Dolls at garage sales often need lots of TLC. If you don't mind cleaning and doing some repair work on dolls, this can be a cheap way to build up your collection.