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