If you are planning to buy a real pearl necklace, then that could be very stressful because if you really want to get a pearl of top quality, there are many questions and steps that one needs to follow so that you can get the pearl of your standard.
Pearls are a pretty and very fashionable accessory to any wardrobe. Below are the questions and some explanations of stpes.

Suppose you want natural pearls, cultured pearls, or imitation pearls. (Note 1: For imitation pearls necklaces, they are just custom jewelry – they are much lower priced than the other two.)
(Note 2: Natural pearls are next to impossible to find in stores, and they are also not that expensive compared to cultured pearls.)
Also you have a decision about the shape of your pearls. You can choose a symmetrical pearl, baroque pearl, or irregular pearl. The spherical shaped pearl is the most expensive and very desirable pearl shape.
The Symmetrical pearls and teardrop-shaped pearls should be even in all ways.
The size of a pearl is a very important issue as far as price is concerned. The relative size of a pearl will affect the price of the pearl necklace because bigger is better and more expensive. Where money is not a lot of an issue, then it only matters about size.
So, depending on how much you wanna spend, you know, do you want the double-strand necklace with the smaller pearls, which are less expensive? Or do you want the single-strand, which is more expensive, necklace with the larger pearls?

When you hold up a pearl to direct light, shining on a flat white surface, it is easy to check. For every pearl, the most important feature is luster. This is easy to describe; if the surface of the pearl is shiny, you can easily see all its features. The best luster is presenting a good contrast between light and dark areas. Luster should present strong and crisp reflections. Your pearl should not look white and cloudy.
What do the pearls ‘orient’ – a subtle play of iridescent rainbows of quality colors? Is the color natural or dyed? The latter is cheaper. More exotic natural colors are better value.
Pearly overtone (Pink tones can increase the price; blues can reduce it). These tones should ideally be uniform and regular in color. Anything other than this is an imperfection. Check that your pearls are clean. There should be no nicks, cracks, pits or discoloration.
If you turn it and examine it, if you turn it again from all sides, the colour, shape, smoothness, and lustre can’t all be different on one pearl.
To test if they are round, roll a strand of pearls on a flat edge. Let the strand of pearls out of the folded piece of paper to make it directly touch the flat edge of a table so they roll a bit on the table edge. Round pearls will roll smoother and more evenly. If the pearls are not round, you will feel it when you roll them on a flat edge – like going over a bump.
There are three things you need to do in order to dupe the ruse that imitations are real pearls. First, take the pearls and run them across the bottom edge of your teeth. A real pearl necklace will feel sandy and grainy. A false pearl will feel smooth.
Try to see and palpate them. Perfect pearls and pearls that feel light when you bounce them in your palms are mostly fakes. Try this: Look at the pearl under a ten-diopter magnifier ( a loupe). The fake pearls appear grainy.
This is a process anyway, and you can do only what you can to determine the value of the pearls. If not, bring a knowledgeable person with you.