When conjugating regular verbs in the present indicative drop the last two letters and change to their appropriate ending. Lets take the verb Hablar as our example. To change to Yo we drop the AR ending and change it to O creating the word HABLO the ending for all three forms will remain an O. For the rest of the verbs we can keep the letter before R. In the case of our verb our stem will now be Habla. The Tu form adds and S giving us the verb Hablas. El/Ella adds no ending so we keep Habla. Nosotros will add mos creating the verb hablamos. Ellos/Ellas/Uds. add a N creating Hablan.
The formula will remain
Yo- (AR, ER, or IR)+O
Tu - R + S
El/Ella - R
Nosotros- R+ mos
Ellos/Ellas/Uds. - R + N
AR
Hablar
Yo-------------------------------Hablo
Tu-------------------------------Hablas
El/Ella---------------------------Habla
Nosotros------------------------Hablamos
Ellos/Ellas/Uds.---------------Hablan
ER
Comer
Yo------------------Como
Tu------------------Comes
El/Ella-------------Come
Nosotros---------Comemos
Uds.---------------Comen
IR
Vivir
Yo----------------------Vivo
Tu---------------------Vives
El/Ella-----------------Vive
Nosotros-------------Vivimos
Uds.-------------------Viven