It's easy for Switzerland: They have no ß.
In capitalized words, the ß is usually replaced by a double-S. There are very few fonts featuring a capital ß, and there's no way to type it. Most germans don't know it exists.
Please note that an ß is not simply two s after one another, it's a different character, which is why Bundes-Straße can never have an ß at the end of Bundes.
Words never start with an ß.
An ß is always sharp, not vocalized (like the english s in ass, unlike the german s, which is very often pronounced like the z in lazy).
Whether or not you use an ß is usually determined by the length of the vowel preceding the s/ß: You never have an ß after a short vowel. For example, muß (must) used to be correct, but since '96, it's muss. Muße (leisure) has a long vowel, so it has an ß.
The ß is also usually found after a diphthong, as in beißen. Probably because diphthongs are usually also long.