Because I'm currently doing a lot of non-programming tasks in emacs the spell-check problem became one of my major concerns once again.

I noticed that there is no question related to the options for spell-checking in emacs yet, so here we go:

What are my options to do spell-checking in emacs?

Specifically,

• for general purpose spell-checking, i.e. sensible suggestions for typos, spell correction of words
• for selective spell-checking, e.g. general purpose spell-check but only in comments
• for heuristic spell-checking, i.e. grammar spell check. Something similar (but hopefully better) to the MS Word spell-checker which recognises if a sentence is grammatically wrong
• for spell-checking in a broader sense, i.e. for improving your phrasing and the expressions you are using. Something along the lines of Dead Poets Societies

So avoid using the word ‘very’ because it’s lazy. A man is not very tired, he is exhausted. Don’t use very sad, use morose. [...]

• for anything which I forgot or am not aware of but you can think of (spell-check related, duh...)