For regular verbs, the passato remoto is formed by adding appropriate endings to the stem of the verb. Following is a chart showing how regular verbs in -are, -ere, and -ire are conjugated in the passato remoto. The added endings are in bold.
amare
vendere
finire
amai
vendei (vendetti)
finii
amasti
vendesti
finisti
amò
vendé (vendette)
finì
amammo
vendemmo
finimmo
amaste
vendeste
finiste
amarono
venderono (vendettero)
finirono
NB: As you can see in the table above, -ere verbs have two sets of possible endings in some persons. It is advisable not to use the endings -etti, -ette, -ettero when the verb stem ends in “t”. For instance: battere (battei), discutere (discutei). As for the rest, there are no set rules and both forms are acceptable.