What is the difference between a good Sunnah and a bad Sunnah, and bid‘ah (innovation) according to the noble Hadith, and how can one avoid bid‘ah?

A good Sunnah (practice/precedent) is when a person initiates an act of obedience, and others follow his example. Whoever does this will receive the reward for his action and the reward of those who emulated him. As for a bad Sunnah, it is when a person initiates an act of disobedience, and others follow his example. He will bear the burden of that sin and the burden of those who emulated him. An example of this is the story of the Ansari man who began giving charity, and people followed suit. Similarly, the first person to initiate killing (the first son of Adam) bears the burden of every soul unjustly killed. As for a good Bid'ah (innovation), it is an act for which there was no precedent, but it is based on a legitimate religious proof. If it is not based on a legitimate religious proof, then it is a blameworthy Bid'ah, because "every Bid'ah is misguidance."