Unfortunately, the arrays of modern whetstone can be bewildering to the inexperienced sharpeners that so often times many of them end up with a crap or wrong decision on stone type for their utensils. The most difficult to determine is whether the whetstone is fake or fabricated with low quality of materials. To avoid this you can only go for the reliable brand of a whetstone.
For woodworking tools like chisels and plane blades, you will need stones that are at least as wide as the blades themselves. Length is helpful but not always critically important. The one exception is when you're using a guide for sharpening tools. The guide often rides on the stone and longer stones permit you to use a much larger portion of the stone as both the guide and the edge need to simultaneously touch the stones.

first time buying a sharping stone. i bought this because i wanted to sharpen kitchen knives. you have to practice to get good at it, use a knife you don't care about because you might mess it up. there is some conflicting instructions online on how to use, water or no water. read as much as you can about using stones and practice, practice , practice. look up videos on youtube and internet. i had fun using it, BUY IF YOU WANT TO LEARN here is some stuff i found, they all sound like professionals http://video.about.com/culinaryarts/Sharpen-Knives-With-a-Whetston.htm?rd=1 http://culinaryarts.about.com/od/knivescutlery/ht/whetstone.htm this is a video that says don't use water http://video.about.com/culinaryarts/Sharpen-Knives-With-a-Whetston.htm?rd=1 this is a youtube video that i watched that uses water. *informative http://www.youtube.com/watch?v=KFIg9Cm-nJg
The stones from Shapton are probably the hardest of all Japanese sharpening stones. They will remain flat for a long time. They are therefore the best choice if you are looking for a relatively coarse stone that cuts quickly without having to be dressed repeatedly. The finer-grained stones also work very well. But Shapton stones do not provide the mirror finish you can achieve with softer stones.

I purchased this set together with the 400/1000 grit stone assuming that some of my knives were quite dull and would need work on a coarse grit stone. Premium Whetstone Sharpening Stone 2 Side Grit 400/1000 | Knife Sharpener Waterstone with NonSlip Rubber Base & Flattening Stone. This is my first wetstone. First off I tried to sharpen my Chicago Cutlery boning knife. This knife is nearly thirty years old, has been abused in may ways and was quite dull. It was very difficult for me to get a burr on this blade, which I attribute to poor technique. Next I moved on to my Henckels Professional S paring and chef's knives. The paring knife was moderately sharp and was modestly improved after working over all three grits of stone. It would cut paper but again it was difficult to develop a burr with this blade. Undaunted I switched to the chef's knife. This knife is twenty years old and has never been professionally re-sharpened. I have sharpened it twice with a Lanksey sharpening system which marred the finish but did put a good edge on the blade. Lansky Standard Coarse Sharpening System with Fine Hones. The chef's knife was moderately dull and had several pits visible on the cutting surface. I modified my technique for passing the knife over the stone and worked the chef's knife over the 400 grit stone aggressively and eventually I was able to get a burr to form from the tip of the knife all the way to the handle. From there it was a simple process of reforming the burr on the 1000 grit stone and then finishing on the 6000. After sharpening, the chef's knife easily and cleanly slices a tomato with very light pressure and is in my opinion very sharp. Not sushi knife sharp but more than enough for the chopping and slicing I expect of it. I'm looking forward to going back and working both the boning knife and the paring knife over again. Don't expect a good result from this product the first time you use it. Watch videos on using a wetstone, expect to spend at least twenty minutes per knife at first, and practice forming a burr. If you can form a burr, you will be able to successfully sharpen your knife.