How to find coupling and decoupling capacitor values?
The reason for decoupling capacitors is to absorb the current gulps which the IC demands. Without the capacitor, you get lots of high frequency noise between the ground and power. This is the why of decoupling.

There are various methods to apply to select your decoupling capacitors. If they are defined it the datasheet, always follow that. If not, you can either "do the maths" based on the frequencies and work our what you need, or you need to apply the engineering rule-of-thumb. A while ago, there was a strong belief in going for "decade" capacitors, using a 10nf, 100nF and 1uF, to get a good range across the frequency spectrum. These days, after lots of work has been done on it, the rule which gets applied most is "largest capacitor in smallest package". So you get the standard package you're using (say 0603 or 0402) and get the largest capacitance you can find in that package with the required voltage rating. This is usually all you need. If you need more decoupling than that, you will need to "do the maths" which will depend so much on your circumstances that it can't be addressed here.



For those interested, the reasoning behind largest capacitance in smallest package: the smallest package has the lowest inductance, and therefore will absorb high frequencies easily. Higher capacitor value, will handle higher amplitude noise.