Some words ending in –ly are adjectives, and not normally adverbs. Examples are: costly, cowardly, deadly, friendly, likely, lively, lonely, silly, miserly and unlikely.

Incorrect: He behaved cowardly.
Correct: He behaved in a cowardly manner.
Correct: He behaved like a coward.

Incorrect: He laughed silly.
Correct: He gave a silly laugh.

Incorrect: He lives miserly.
Correct: He lives in a miserly way.

In the sentences given above the words cowardly, silly and miserly are all adjectives which cannot be used to modify verbs. And because there are no adverbs for these meanings we have to use adverb phrases like ‘in a cowardly manner’ and ‘in a miserly way’ to express the same idea.

Incorrect: Just I had gone when he came.
Correct: I had just gone when he came.

Incorrect: Still I love you.
Correct: I still love you.

The adverbs still and just go before the verb. If there is an auxiliary verb, the adverb goes after the auxiliary verb and before the main verb. If there is no auxiliary verb, the adverb goes before the main verb. If there are two auxiliary verbs, the adverb goes between them.

I am still waiting for your reply. (NOT I still am waiting for your reply.) (NOT I am waiting still for your reply.)
They have just been informed. (NOT They have been just informed.)
She has just arrived. (NOT She just has arrived.)