1 Most of the adverbs follow the verb they modify.
Felipe canta bien.
Me encuentro mal.
Except in rhetorical or emphatic use of the language.
Mucho ha llovido desde entonces.
Antes tenías que haberlo dicho.
2 Between the auxiliary verb and the past participle there are not place for an adverb. The adverb follows or precedes the verb.
Siempre te he escuchado.
Me han tratado mal siempre.
3 Some adverbs appear always before the verb: apenas, casi, no, etc.
Apenas veo la pantalla desde esta butaca. (= I hardly see the screen.)
Casi me caigo. (= But I did not fall.)
No tengo dinero.
4 The position of the adverb solo and its synonyms solamente and únicamente determines the clause meaning.
Solo yo le pegué.(= Neither John nor Marcelo beat him.)
Yo solo le pegué. (= But I did not shoot him, nor did I stabbed.)
5 The adverb precedes adjectives, past participles or other adverbs when modifying them.
Eres muy guapa.
Es bastante pronto.
Felipe canta bastante bien.
El Madrid juega muy bien.