Make sure the Beanie Baby you are about to buy is an authentic Ty product, before you spend money on it. The first Beanie Babies were created in 1986, but they did not become a household name until 1996 --- at which time they became the most popular children's toy and collectable. Beanie Babies sold by collectors should specify that they have been "authenticated," which means they have been determined to be authentic Ty products by a reputable authentication service. If not, there are some ways you can determine yourself if the toy is a fake.
Refer to a Beanie Baby expert website that has an illustrated reference guide for how the "hang tags" should look for the generations of Beanie Babies. The heart-shaped hang tags vary from generation to generation, so you should compare the pictures online with the Beanie Babies for sale or carry a printout of the pictures with you.
Feel and visually examine the heart-shaped "Ty logo tag" attached to the toy's ear. If the gold foil lining around the edge of the front of the tag has slight wrinkles or an uneven appearance, the toy is not authentic. Authentic Beanie Babies have a perfectly smooth, even gold lining on the tags. Look at the hole in the tag --- if it has a smooth edge, it is authentic.
Check the "tush tag" or fabric tab on the rear seam of the toy to determine if it is still intact (Beanie Babies that have been given to children may have had the tags removed). An authentic Beanie Baby has its name printed on the tag in red, without a space between the name and the TM Trademark symbol. Some fakes have the name printed in orange, with a space between the name and the TM symbol. The name may even be misspelled.
Examine the colour, weight and proportion of the Beanie Baby itself and compare it to pictures of the authenticated version of the same one. Fake Beanie Babies tend to be overstuffed and heavier than the real ones, are often a slightly different colour or are poorly made in general. For example, one of the legs might be slightly smaller than the other.