While amber may come from many places in the world besides the Baltic regions, such as Ukraine, and and especially China (probably the source for half the world's amber), amber is usually associated with Lithuania.

Some people will tell you of a "heated pin" test where a hot pin is touched to amber, releasing some of it's aromatic incense-like, and characteristic smell.  However, if you were to spark a lighter and take out a pin in a shop, you would certainly be chased out. This will leave a mark on the piece, which is undesirable. Besides, any good shop would never deal in fake amber.

But if you have a piece of amber, or strung, or even sometimes in a pin or brooch, this test will prove the difference between real amber, and plastic fakes.

A fact is that amber floats in sea water.  A large pot, or bowl filled with brine, or very salty water can be used for this test.  Simply put the piece of amber in the brine, and watch... amber will float, plastic will stay on te bottom, due to it's being denser (heavier) than water.  Sometimes even strung amber, or some set in jewelry will even show some buoyancy on the bottom or the container.  This test also works in a glass of coca-cola, interestingly enough - but NOT in diet coke.

If you want to determine where a piece of amber is from, there is also a test for this.  Unfortunately, this test is done by InfraRed spectroscopy, which can determine whether or not a piece of amber is from the Baltic region, or just somewhere else in the world. You'd  have to go to a special lab, but if you were buying a spectacularly expensive piece, it could be worth the cost.