Derived adverbs are formed by adding the ending e to the stem.
E.g.: bone – well, kuŝe – lying, facile – easily, rapide – fast, quickly, ekzakte – exactly, blue – bluely, sabate – on Saturday, nokte – in the night, skribe – in writing
Many of them are derived from prepositions:
antataŭ – before ◊ antataŭe – ahead
apud – beside ◊ apude – nearby (adv.)
dum – during ◊ dume – in the meantime
ekster – outside of ◊ ekstere – outside
kontraŭ – against ◊ kontraŭe – vice versa, conversely
kun – with ◊ kune – together
post – after ◊ poste – afterward
sub – under ◊ sube – down
super – above ◊ supere – above (adv.).

Many of the adverbs are not derived, so called primitive.

EG: nun – now, jam – already, ĉi – near to me, ankoraŭ – still, baldaŭ – soon, hodiaŭ – today, tuj – immediately, plu – more, tre – very, ankaŭ – also, do – thus, nur – only

Some adverbs are part of the system of so called correlatives (see chapter 3.6)

Comparison of adverbs is done analytically. Comparative is formed by pli + positive, superlative by plej + positive.

Mi faras tiel bone kiel vi. – I work as good as you.
Mi faras pli bone kiel vi. – I work better than you do.
Mi faras plej bone el ni. – I work best from us.
It is also possible to compare in opposite direction using prefix mal – then comparative is formed by malpli + positive, superlative by malplej + positive. It is equivalent to put prefix to the adverb pli/plej and to the compared adverb.

Vi estas malpli bela ol ŝi. = Vi estas pli malbela ol ŝi. – You are uglier than she is.
Vi estas malplej bela ol ni. = Vi estas plej malbela ol ni. – You are the ugliest from us.
Adjectives compare the same way (see 3.4.2)

Adverbs of place can form accusative to mark the direction.
hejme – at home (place): Mi estas hejme. – I am home.
hejmen – at home (direction): Mi iras hejmen. – I go home.
kie – where (place): Kie vi estas? – Where are you?
kien – where (direction):  Kien vi kuras? – Where do you run?