To form the present participle, simply add -d to the infinitive. It usually functions as an adjective and takes the normal adjective endings. It can also function as an adverb, but then of course, it does not add any endings.
kochendes Wasser - boiling water
die führenden Kritiker - the leading critics
im kommenden Sommer - in the coming summer
Sie spricht fließend Deutsch. She speaks German fluently.
