1) For all -ER verbs, including stem-changing verbs and the normally irregular verb aller, take the third person singular form of the passé simple as the stem and add the imperfect subjunctive endings. Note that spelling-change verbs like manger and lancer have their spelling irregularity in all of these conjugations.
2) For -IR verbs, -RE verbs, and irregular verbs, the imperfect subjunctive is formed as follows: third person singular form of the passé simple minus the final t, plus the imperfect subjunctive endings.
Here are the imperfect subjunctive endings and conjugations for the -ER verbs parler (to speak), manger (to eat), lancer (to throw), and aller (to go), the regular -IR and -RE verbs finir (to finish) and rendre (to return), and the irregular verbs avoir (to have) and venir (to come):
French imperfect subjunctive conjugations
| parler | manger | lancer | aller | |||
| 3rd person singular passé simple | il parla | il mangea | il lança | il alla | ||
| Imperfect subjunctive stem | parla- | mangea- | lança- | alla- | ||
| Pronoun | Ending | |||||
| ...que je | -sse | parlasse | mangeasse | lançasse | allasse | |
| ...que tu | -sses | parlasses | mangeasses | lançasses | allasses | |
| ...qu'il | -^t | parlât | mangeât | lançât | allât | |
| ...que nous | -ssions | parlassions | mangeassions | lançassions | allassions | |
| ...que vous | -ssiez | parlassiez | mangeassiez | lançassiez | allassiez | |
| ...qu'ils | -ssent | parlassent | mangeassent | lançassent | allassent | |
| finir | rendre | avoir | venir | |||
| 3rd person singular passé simple | il finit | il rendit | il eut | il vint | ||
| Imperfect subjunctive stem | fini- | rendi- | eu- | vin- | ||
| Pronoun | Ending | |||||
| ...que je | -sse | finisse | rendisse | eusse | vinsse | |
| ...que tu | -sses | finisses | rendisses | eusses | vinsses | |
| ...qu'il | -^t | finît | rendît | eût | vînt | |
| ...que nous | -ssions | finissions | rendissions | eussions | vinssions | |
| ...que vous | -ssiez | finissiez | rendissiez | eussiez | vinssiez | |
| ...qu'ils | -ssent | finissent | rendissent | eussent | vinssent | |




