By adding –ly to an adjective:

Strange, strangely; brave, bravely; beautiful, beautifully; able, ably; cheerful, cheerfully; modest, modestly; probable, probably; selfish, selfishly; vigorous, vigorously

She is a beautiful girl. (Adjective – beautiful)
She smiled beautifully. (Adverb – beautifully)
He is a brave man. (Adjective – brave)
He fought bravely. (Adverbs – bravely)
He is a strange person. (Adjective – strange)
He behaved strangely. (Adverb – strangely)

By adding the suffixes wise, ways, ward and wards

She glanced sideways at the visitor.
I looked upwards.
Let’s march forward.
He crawled crab-wise across the floor.

Note that most of these words can be used both as adverbs and adjectives. For instance, we can speak of an upward trend (Here upward is an adjective qualifying the noun trend) or a sideways glance (Here sideways is an adjectives qualifying the noun glance.).

Some compounds made of a preposition and a noun are adverbs.

Examples are: afoot (on foot), abed, aboard, ahead, away, besides, today, tomorrow etc.

Some compounds made of a preposition and an adjective are adverbs.

Examples are: abroad, along, aloud, around, anew, behind, below etc.

Some compounds made of an adverb and a preposition are also adverbs:

Examples are: hereafter, hereby, herein, wherefore, thereupon, therein, henceforth etc.

Words used as both adjectives and adverbs

Some words can be used both as adjectives and adverbs. Examples are: early, easy, daily, leisurely etc.

He is an early riser. (Here early is used as an adjective qualifying the noun riser.)
I got up early today. (Here early is used as an adverb qualifying the verb got up.)
It is an easy job. (Here easy is used as an adjective qualifying the noun job.)
Take it easy. (Here easy is used as an adverb qualifying the verb take.)

Adverb phrases

Read the sentences given below:

He drives carefully.
He drives with care.

Here carefully is an adverb showing the manner in which he drives. With care is a phrase which means the same as carefully and does the work of an adverb. Hence it is an adverb phrase. It is possible to substitute an adverb phrase for an adverb.

Most adverb phrases begin with a preposition. Note that not all adverbs can be changed into an adverb phrase or vice versa.

He fought courageously.
He fought with courage.
She searched everywhere.
She searched all over the place.
He looked at me suspiciously.
He looked at me with suspicion.
The workers hurried towards their homes.
The workers hurried homeward.