Position of adverbs in Spanish sentences
Can someone tell me about adverbs in Spanish sentences, specifically where are they placed in sentences? For example, he runs quickly, he is very tall, they are very high mountains, the mountains are very beautiful. Can someone give me the correct Spanish sentences for the above? Are there grammatical rules to follow?
4 Answers
As savvyspanish says, the position of the adverb in Spanish is very similar to English, except in a few minor cases:
1) In perfect tenses (haber/to have + verb), in English adverbs often go in between, e.g. "I have already seen it", but in Spanish these two parts of the verb can never be split like that, so that is a position where the adverb cannot appear.
2) Spanish is more flexible than English in terms of word order, so adverbs generally can appear anywhere, provided that they don't split phrases. Some alternatives may sound a bit weird, but they are not necessarily wrong:
Ayer vino mi hermano - Perfect; "ayer" is a key piece of information here
Ayer mi hearmano vino - Not very common; it is unusual to leave the verb at the end like that
Vino ayer mi hermano - Not so common; elements are introduced in an unexpected order
Vino mi hermano ayer- Less common; "ayer" seems to be secondary here
Mi hermano vino ayer - Perfect
Mi hermano ayer vino - Weird... but not wrong
Of the examples you provided, the first one is different than the other 3. In the first example, the adverb modifies the verb and comes after the verb.
He runs quickly= él corre rápido
In these 3 examples, "very"/"muy" is an adverb of degree and modifies an adjective. These adverbs usually come before the adjective in the sentence.
He is very tall= él es muy alto The mountains are very high= Las montañas son muy altas The mountains are very beautiful= Las montañas son muy bonitas.
The nice thing is that the word order here is very similar to English, so that makes it easier. Keep practicing and this will all come naturally to you one day! 
Corre rápido. = He runs quickly.
He is very tall (no adverb)
They are very high mountains (no adverb)
The mountains are very beautiful (no adverb)
Of your examples, only the first has an adverb. When an adverb modifies a verb, it usually follows the verb.
An adverb usually follows the verb it modifies. But if an adverb modifies an adjective or another adverb, then it goes before, or precedes it.
Here is an article covering the use of adverbs, including their placement in a sentence.
