Adverbs are usually made from adjectives, by adding -LY. However, there are some exceptions. These are the rules:

Adjective ending in...	How to make the adverb	Examples
y	Change Y to I and add -LY	heavy - heavily happy - happily lazy - lazily
[anything else]	Just add -LY	warm - warmly nice - nicely loud - loudly

However, there are some important exceptions:

Adjective	Adverb
good	well
late	late ("Lately" means recently. It is not the adverb from "late".)
early	early
fast	fast
hard	hard ("Hardly" means not much. It is not the adverb from "hard".)