Unlike the regular yer, or "hard sign" in Russian, the separation performed by the soft sign is only partial, meaning that it changes the sound of both the letters before and after it. This is why in Russian it is more orthographically correct to write подъезд (pod'yezd), the porch, than подьезд (podjyezd), where the д would be pronounced as [dje].
Among Slavic languages, soft sign has the most limited use in Bulgarian: since 1945, the only possible position is one between consonants and 'o' (for example, in names Жельо, Кръстьо, Гьончо etc.).
The Cyrillic variant of the Serbo-Croatian language (Vukovica) has had no soft sign since mid-19th century: palatalization is represented by special consonant letters instead of this sign (some of these letters, such as Њ or Љ, were designed as ligatures with the soft sign). The modern Macedonian writing system, created in 1944 and based on the Serbo-Croatian variant, has had no soft sign from the very beginning.
No words start with it, and under normal orthographic rules it has no uppercase form. However, Cyrillic type fonts do normally provide an uppercase form for setting type in all caps, or for using it as element of various serial numbers (like series of Soviet banknotes) and indices (for example, there existed model of old Russian steam locomotives marked "Ь").
In the romanization of Cyrillic words, soft signs are typically replaced with the prime symbol (or, alternatively, apostrophe) or just ignored (especially in the final position: Тверь=Tver, Обь=Ob etc.).