One of the first things you want to see the artist mention, is that they have used artist quality paints. This should always be stated, and often the brands are given as well! You will see many brands as watercolorists all vary in what they prefer - but you may see names like Winsor and Newton, Daniel Smith, M. Graham, and Holbein.
The next thing to consider is the weight of the paper. The paper will greatly determine the look and feel of the painting and, again, different artists have different preferences in the maker. But a quality watercolor is always painted on 140lb or 300lb. Anything lower and the paper is going to be thin and of very low quality.
(c) Jean Hood
Then you may want to look for certain techniques that show you the artist has studied and understands watercolor! Here's are two great examples of negative painting - painting in the background to bring forward an object.
(c) Jean Hood
Now there are some very unusual techniques you can also look for in a watercolor painting. The use of some sort of masking allows a painter to keep an area unpainted or painted over without taking color. There are also artists who use paint spattering as great way to bring texture and movement to their artwork. You can see examples of these techniques in these two paintings:
Another thing to consider as you look at watercolor paintings, are some of the more unusual surfaces that can be used. Here is an example of a type of rice paper, that is wetted, crumpled, then flatted and painted. It creates this wonderful batik type look!
Then there is Yupo. Yupo is a synthetic paper, which means that the paint simply floats on top! It's hard to paint on with watercolor because it can just wipe off with a bit of water, but it creates some fantastic looks!!! After it's been painted, it must be sealed with a spray sealant. Here's an abstract example of a Yupo watercolor painting. This artist not only painted the yupo, but also carefully removed certain areas of paint with water, before sealing the painting.
Lastly, stetched canvas has often been consider only an oil or acrylic surface! But recently there are two companies that have come out with canvas that can be painted on with watercolor! (Fredrix and YES!) These too, have a bit of different look, and must also be sealed with a spray sealant, but now, watercolor can be painted on gallery canvas just like the oils and acrylics!
We have a large variety of painters on the Design Style team. Click here to see a search of all the artists offering watercolor paintings on Etsy!