Re: By pass caps
All your PCB traces conducting current acts as antennaes picking up noise. So to avoid the noise affecting your IC supply pins, you place a capacitor very close to that pin, as the high frequency noise then will se a low impedance path to ground, choosing that path instead of going through your IC. Remember that all traces also have an inductance; the thinner and longer the trace the higher inductance. The same goes for capacitor leads. This inductance results in a higher impedance at high frequencies, thus reducing the effect of your bypass cap. So in noise critical applications, you would want to choose SMD capacitors (as they have no leads), with a short and thick trace to the supply pin.