If you're planning to pop the question on Valentine's Day, then you're not alone.  According to the Diamond Information Center, some 220,000 men (and women) get down on one knee during this romantic holiday each year, marking February 14th as the most popular day for couples to get engaged in the United States.

With each proposal usually shines a diamond ring, and depending on the cut, carat, color and clarity, this particular Valentine surprise could be the most expensive you've orchestrated yet.  If you don't know what to look for or how to price out a rock, review these six basic diamond buying tips so you don't blow your entire bank account.

1. Research Pays

Before you begin the buying process, learn about the four Cs: cut, carat, color and clarity. The unnamed fifth C, naturally, is cost. Read The Diamond Buying Guide for details and don't forget to chat with your significant other about personal preferences before making the purchase plunge.

2. Cash Out

Diamonds are forever on your credit card. Don't let a seller talk you into a more-expensive stone by quoting monthly payments. The interest rates will make the total payments seemingly stretch into infinity. Wait until you can afford to pay cash while saving even more money when you buy store gift cards at up to 50 percent off the face value from websites like GiftCardGranny.

3. Never Buy Sight Unseen

Photographs just don't tell the whole story. If you plan on buying a diamond ring off of Craigslist or another website, have a qualified jeweler examine the stone and setting before you hand over your hard-earned money.

4. Size Isn't Everything

The biggest determinant of diamond price and beauty is the cut, not carat weight or size. Examine stones with a variety of cut grades to understand what qualifies as a well-cut and affordable diamond.

5. Get a Report Card

Make sure your rock comes with a diamond-grading report. You'll enjoy more peace of mind if you have an independent professional lab verify the quality.

6. DIY

Purchase a diamond wholesale, then allow your fiancée to select the desired setting. Not only will you save on the overall cost, but you will avoid potential sad scenes since personal style preference plays a major role in the dream engagement ring.

Andrea Woroch is a consumer and money-saving expert for Kinoli Inc. As a nationally recognized media source, Andrea has been featured among top news outlets such as Good Morning America, NBC's Today, MSNBC, New York Times, Kiplinger Personal Finance, CNNMoney and many more.