You need the right size of sharpening stone that fit the type and size of your blades and tools. In general, 6-inches stones are the smaller models and 8-inches are the larger ones. The stones larger than 8 inches are work best for big-sized blades and tools. You may also find sort of ‘pocket knife sharpener’ out there. Most of the credit card sized sharpening stone are smaller than 6 inches and ideal for on the go sharpening not for regular basis.
The DuoSharp Plus stones are nicely sized at 8” long by 2 5/8” wide and have two grits on each stone to maximize value. The Plus in the name refers to an area of continuous grit in the otherwise interrupted grit surface of the stone. This area is for sharpening edges with fine points that might be difficult on the interrupted surface. A coarse/fine DuoSharp Plus stone is a good single stone to start a sharpening toolkit.
Once the burr is removed, it's time to test the sharpness with paper. Hold a piece of newspaper at about 45°, with a bit of tension, and slash lightly with each point of the blade. If it cuts through easily, your knife's sharp. Warner speedily lacerated his newspaper, but I of course struggled. There is an element of technique involved, he reassured me. 
Different knives are sharpened differently according to grind (edge geometry) and application. For example, surgical scalpels are extremely sharp but fragile, and are generally disposed of, rather than sharpened, after use. Straight razors used for shaving must cut with minimal pressure, and thus must be very sharp with a small angle and often a hollow grind. Typically these are stropped daily or more often. Kitchen knives are less sharp, and generally cut by slicing rather than just pressing, and are steeled daily. At the other extreme, an axe for chopping wood will be less sharp still, and is primarily used to split wood by chopping, not by slicing, and may be reground but will not be sharpened daily. In general, but not always, the harder the material to be cut, the higher (duller) the angle of the edge.

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The basic concept of sharpening is simple – you're using an abrasive edge to remove metal – but the knife you buy may alter the method you should use. A general rule of thumb is that a waterstone can be used for both Japanese- and Western-style blades, but you should avoid pull-through sharpeners for Japanese knives (or any knife with very brittle blades).
In addition, the most prized of the natural Japanese Water Stones are quarried in the Narutaki District north of Kyoto, Japan and are commonly available as either bench stones or pocket stones in grits ranging from 120 to 12,000. On the other hand, synthetic water stones are made from Aluminum Oxide and commonly available as either bench stones or pocket stones as well in grits ranging from 220 to 8,000 and, although this is the same abrasive material used to make India Oil Stones, the difference between the two is that the binder that holds the abrasive together enables Water Stones to be much softer than India Oil Stones which, in turn, promotes faster cutting because the worn abrasive material breaks away more quickly and is replaced with fresh, sharp, abrasive material more quickly. In addition, because water stones do not become glazed or loaded with swarf like oil stones can, new abrasive particles are constantly exposed as the stone wears so it continues to cut consistently. Plus, they can be lubricated effectively with water (rather than oil which can ruin some water stones) which combines with the fine particles of abrasive from the surface of the stone to form a slurry which polishes the bevel as the stone cuts. However, it should also be noted that Water Stones do become uneven significantly faster than other types of whetstones although, their softness does make them easier to true again.