Tim Bowen's discussion of the grammar of this persistent little word proves that he really is ever so clever.
The main use of ever is its use as an adverb (mainly in negatives or questions) to refer to any time in the past, present or future, as in ‘Was he ever in the army?’ or ‘If you ever need any help, just let me know’. It is also found in the expression if ever, which usually follows seldom or rarely, as in ‘The method rarely, if ever, fails’.
Ever can also be used for emphasis with comparatives and superlatives, e.g. ‘Isabel’s looking lovelier than ever' and ‘Thailand’s largest ever trade fair’. It can also be used with so and such to mean very, as in ‘It was ever so kind of you to invite us’ and ‘She’s ever such a good dancer’. The expression as ever is used for saying that someone’s behaviour or a situation is the same as usual, or the same as it always has been, e.g. ‘Gordon, as ever, tried to make difficulties’. Ever since refers to the whole period of time since something happened, as in ‘I first met Harry at high school and we’ve been friends ever since', and for future reference, if talking about a situation that will continue for a long time, the expression for ever can be used, e.g. ‘It looks as though we’ll be stuck here for ever; the road’s still blocked’.
Ever can also function as a prefix to mean always or continuously and is followed either by adjectives or the present participle and separated from them by a hyphen. Examples include ‘… paintings by the ever-popular Van Gogh’, ‘the ever-changing countryside’ and ‘ever-increasing numbers of students’.