There are 2 forms of the imperfect subjunctive, which are used indistinctly.

1) The first is formed by taking the 3rd person plural of the preterite minus -on.

For the verb hablar, the third person plural of the preterite is hablaron, removing the "on" yields hablar. To this stem you add the following endings:

-a -amos
-as -ais
-a -an

hablar (full conjugation)

yo	hablara	(I spoke)
tú	hablaras	(you spoke)
Ud./él/ ella	hablara	(you/he/she spoke)
nosotros (as)	habláramos	(we spoke)
vosotros (as)	hablarais	(you guys spoke)
Uds./ellos/ ellas	hablaran	(you all/they spoke)

For the verb "comer", the third person plural of the preterite is "comieron", removing the "on" yields "comier". To this stem you add the following endings: -a, -as, -a, -amos, -ais, -an.

comer (example sentences) (full conjugation)

yo	comiera	(I ate)
tú	comieras	(you ate)
Ud./él/ ella	comiera	(you/he/she ate)
nosotros (as)	comiéramos	(we ate)
vosotros (as)	comierais	(you guys ate)
Uds./ellos/ ellas	comieran	(you all/they ate)

For the verb "vivir", the third person plural of the preterite is "vivieron", removing the "on" yields "vivier". To this stem you add the following endings: -a, -as, -a, -amos, -ais, -an.

vivir (example sentences) (full conjugation)

yo	viviera	(I lived)
tú	vivieras	(you lived)
Ud./él/ ella	viviera	(you/he/she lived)
nosotros (as)	viviéramos	(we lived)
vosotros (as)	vivierais	(you guys lived)
Uds./ellos/ ellas	vivieran	(you all/they lived)

2) The second is formed by taking the third person plural form of the preterit (e.g., hablaron), minus -ron from the end.

For the verb hablar, the third person plural of the preterite is hablaron, removing the "ron" yields habla. To this stem you add the following endings:

-se -semos
-ses -seis
-se -sen

hablase hablásemos
hablases hablaseis
hablase hablasen

bebiese bebiésemos
bebieses bebieseis
bebiese bebiesen

viviese viviésemos
vivieses vivieseis
viviese viviesen