Grammar

amo/ I love, amare/to love, amavi/ I had loved, amatus/ loved
sedeo/ I sit, sedere/ to sit, sedi/ I have sat, sessurus/ sitting
curro/ I run, currere/ to run, cucurri/ I have ran, cursurus/ running
audio/ I hear, audire/ to hear, audi/ I have heard, auditus/ hearing

ere in the infinitive....
if first principal part end in -eo then 2nd
if not 3rd

narro, narrare, naravi, naratus 1st
sedeo, sedere, sedei, sedetus 2nd
arcesseo, arcessere, arcessei, arcessus 2nd
puto, putare, putavi, putatus 1st
nuntio, nuntiare, nuntavi, nuntatus 1st
accipio, accipere, accipei, accipetus 3rd
persuadeo, persuadere, persuadi, persuaditus 2nd
sto, stare, stavi, status 1st
debeo, debere, debi, debitus 2nd
possum, posse, potui, potorus irregular
perio, perire, peti, petitus 4th