On average, gentlemen famously spend in the ballpark of two months' salary on engagement rings for their brides-to-be.

The average price of the tiny-crystals-of-carbon love token is currently $2,750, according to Amanda Gizzi, spokeswoman for Jewelry Information Center, a non-profit trade organization based in New York.

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So just as when you’re looking to put your money in the markets, you should do your homework before making this long-term investment.

Here are some tips:

1. Familiarize yourself with the four Cs: cut, color, carat and clarity.

2. Although she might not like this advice, don’t feel rushed. Take your time, look around and educate yourself.

“Collect pictures of rings that you like, and make a [diamond] expert understand what strikes you. Learn a little of the vocabulary, how to use a loupe [a small magnifying-glass eyepiece used to examine diamonds]” said T. Paul Powell, a 25-year-old program director who recently bought a ring.

3. The most important thing to remember when buying her a diamond is ... her. Know what shape she likes, whether it be cushion, emerald, asscher, pear, marquis, oval, radiant or princess. And make sure the ring reflects her personal style and lifestyle.

"The engagement ring and wedding band are the two things she will wear every day for the rest of her life. If men are still looking to surprise her with a ring, they should take a look at her current jewelry wardrobe and pay attention — I guarantee she will be giving hints,” Gizzi said.

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