Adverbs answer in advance the question "how", or "when", or "where", or "to what extent", or "why", by giving such replies as "precisely ", " today ", " here ", " completely", and "consequently". There are also "adverbs of assertion" (e.g. "yes ", " no " , "perhaps") and "introductory adverbs" (e.g. "accordingly ", " however").
But your reader is often uninterested in the answers to these questions, especially when you answer in an uncertain voice with some invertebrate adverb like unduly or substantially. The bare statement is all he wants. What has been said under the heading Adjectives is equally true of adverbs. Be sparing of them, and use them to give precision rather than to add emphasis. Distrust all those that vaguely intensify, such as very, considerably, appreciably, unduly and substantially, and those that vaguely mitigate such as relatively, comparatively, duly, somewhat, rather. The unreflecting use of very is a bad habit easily acquired.
So is the insertion of necessarily or inevitably into a plain statement of fact. Inevitably is much in vogue just now. It adds nothing in these examples :
The Committees will inevitably have a part to play in the development of the service.
The ultimate power of control which flows inevitably from the agency relationship.
See Relatively, Respectively, Unduly, Very.
On the position of adverbs, see Even, Only, Split Infinitive.