• Asking her about rings in general.

If you're going past a jewelery store pretend to be interested in a watch. Then casually drop a comment about the styles of rings, saying you like a certain type and asking her what she likes. If you're very good, she won't notice the ruse. If you're not so good, she'll probably tweak but she still won't know when! Other ways of getting her to talk about engagement rings is to make a comment about a friend's engagement ring and to ask her preferences at the same time. 

• Ask her family for ideas. This will depend on whether or not you want them to know before she does, of course. 

• Another ruse is to have her friends take her into a store to ask her "just for fun". You'll need to have absolute trust in them to keep quiet and to pull this off. It's not a good option if you'd prefer to keep it quiet until the moment of the proposal. 

• Sum up her tastes from the clothes she wears and her existing jewelery. Your in the best position to know whether she likes plain, fancy, patterns, large or small fashion statements. Is she traditional, classic, contemporary, or way out there? Use what you do know about her fashion preferences to your own advantage. 

• Is she an impassioned supporter of Fair Trade and human rights? Be sure to look for recycled gold and conflict-free diamonds as part of your choosing process. 

Fix your budget. 

There is a tradition that holds that a man should spend two months of his salary on the engagement ring. Whether or not you do this will depend on your wish to conform to tradition. What does matter is that you select a ring according to what you can afford, so have a good idea of this amount before searching. 

• Let your jeweler know your price range so that he or she can show you a variety of rings that fall within that range. 

• Keep in mind the possibility of having an engagement ring customized. Talk to the jeweler about the price options, the timing, and the styles that are possible. 

The durability of the band is important, as constant rubbing and knocking from daily activities will eventually wear down the band. And office work is a killer, with paper acting as a mild abrasive on gold bands. If you can afford it, platinum is the preferred choice for wedding bands as it is more durable than gold. [3] Titanium and steel are also fairly resistant, while the purer the gold, the softer it is and more prone to wearing. 

Know your diamonds. 

Diamonds tend to be the traditional engagement ring choice, because they are enduring, and match everything. Only deviate from a diamond if you know that your girlfriend loves another stone much, much more, or has voiced her intense dislike of diamonds. When choosing a diamond, be aware of the "Four C's", as follows: 

• Carat : This refers to the unit measurement of the diamond, and refers to weight (not size). Every carat has 100 points. Engagement rings are often 1 carat but the ring you choose will obviously depend on your budget. A 1 carat ring on a limited budget may not rate very highly in other areas, taking away from its overall beauty. 

• Color : The color of diamonds varies considerably and most people prefer a very white colored diamond for an engagement ring. Colors are graded from D (colorless and rare) and most good quality diamonds will be around F and H and grades D to I are acceptable to buy as they are almost identical when mounted. 

• Clarity : Being natural, there will be imperfections in the diamond. The less imperfections, the greater the clarity and the more light is reflected from the diamond, causing it to "sparkle". Naturally, more clarity increases its value. Perfectly flawless diamonds with no internal flaws or surface blemishes are very hard to find as they are extremely rare. Fewer flaws in a diamond result in greater brilliance as more light is reflected. [4] 

o The scale used to grade clarity goes from F1 for a flawless diamond, to VVS1 and VVS2 for very slight inclusions, to VS1 and VS2 for very slight inclusions, SI1 and SI2 for slight inclusions and I1, I2 and I3 for imperfect diamonds. 

o Diamonds are magnified by 10 times to judge their clarity so very slight imperfections are difficult to see with the naked eye. This means that there is a range of diamonds available even for more modest budgets. If you can see a mark without magnification, however, think carefully before you buy. The location and darkness of an imperfection of any given grade (though probably not any "VVS" inclusion, which is simply too small, and rarely a VS inclusion) can affect its visibility so it is safest to see the imperfection magnified or in a magnified photograph before buying. 

• Cut : There are different ways to cut a diamond, and the type of cut impacts the sparkle of the diamond. The cut that produces the most sparkle is the round (or brilliant) cut, while radiant and princess cuts are good at hiding flaws. Other cuts including square, emerald, pear, marquise, cushion, ssscher, and heart-shaped. [5] The oval shape looks best with larger stones, and looks bigger than the round cut. [6] A high-quality cut (not necessarily above "Ideal") is more important than weight or an extremely high clarity or color grade: a diamond, like a road reflector, shines light back out the direction it came in and breaks it up a bit in the process. If the sides are ground at the wrong angles (sometimes through less-than-perfect workmanship, sometimes to increase weight with extra width or depth) quite a bit of light will not shine back out the right way--much more than would be lost to a very faint yellowish or brown tint or a speck visible under a loupe. It is also important to base your selection of diamonds based on objective data such as ASET or Idealscope images that you can acquire from your jeweler. [7] This is particularly important if you are buying a diamond engagement ring online. 

Decide by how it looks. Once you've covered the cost, the durability and the practicality of the ring, it's down to how the ring looks. 

• Look for a ring that is out of the ordinary. This isn't an everyday ring; it's the engagement ring, the ring your beloved will treasure lifelong and wear most days for the rest of your life together. 

• If you're choosing one together, let your girlfriend have the final say. 

Purchase the ring. Collect it just before the proposal. That way you can avoid worrying about keeping it safely. 

• Be sure to check that your insurance covers its loss, or ask for insurance from the jeweler's store if available. 

• Ask for a certificate of authenticity and a warranty to accompany the ring. Certificates are very useful to collect with a diamond to find out exactly where they originated from. They are usually only available with the purchase of diamonds larger than just under 1 carat. For smaller diamonds, a certificate would add a considerable amount to the cost of the stone as you may end up paying an extra several hundreds of dollars or pounds to obtain one. 

• Insure! The ring is likely to be the most expensive piece of jewelry you have ever bought, and the most expensive piece of jewelry your fiance (we hope) has ever worn. To prevent her from having to give it up for appraisal and insurance when she's just getting used to wearing it, get it done before you pop the question. 

• Set off - it's time to propose! 

• Referance http://www.wikihow.com/Choose-an-Engagement-Ring