asking about adverbs adverbs

hello dear sir
iam student of department of English in Libya.I would like to ask about adverbs.My question is : What are the difficulties which face students and people in using adverbs?

[Tdol]

They have to be careful with the position; whether they come before or after a verb, and have to remember that adverbs have many functions:
modify verbs (time, frequency, degree and manner)
modify adjectives and adverbs
modify sentences

Here's a quick guide:
http://www.usingenglish.com/glossary/adverb.html