Practice holding the knife at a 20 degree angle. Most straight blades need to be sharpened at a 20 degree angle. To find the angle, hold the directly in front of you so it's straight up and down. This is 90 degrees. Tilt the knife halfway towards the table so it's at a 45 degree angle. Tilt the knife halfway again so it's about an inch (2.5 cm) above the table. This should be a 20 degree angle.[4] 

However, it should also be noted that “water stones” are generally significantly softer than oil stones and thus, water stones generally cut faster than oil stones but, they also have to be flattened more often that oil stones do. Furthermore, it should be noted that some water stones must be soaked in water for several hours prior to use whereas, others are of the “splash and sharpen” variety and thus, they only need to be soaked for a few minutes before use and then wetted down occasionally during sharpening process. Diamond hones on the other hand are more durable than either water stones or oil stones and, because they generally have a more coarse grit, they cut faster than natural whetstones. Plus, due to their construction, they never need truing and, in fact, coarse diamond hones are often used to flatten both natural and synthetic whetstones.
Our large selection of stones from many well-known manufacturers will allow connoisseurs to find the ideal stone for their needs. Because all manufacturers formulate their stones to emphasize a different mix of qualities, and because these qualities can vary widely between different stones, most woodworkers choose stones from several manufacturers to build up an optimal set of sharpening stones. Then again, once you get to know the characteristics of certain types of stone, you may find one supplier who will provide all the stones you need. Sometimes this can be an advantage. But there is no one size that fits all; each stone must fit your needs and work style.