To conjugate verbs in the conditionnel and futur simple, you must use the verb in its infinitive form and tack the imparfait endings to the conditionnel and the AVoir endings to the futur simple. As you know that there are number of exceptions for this rule which I will deal with later.

Conditionnel: example; La demoiselle arrive tres tot chaque matin. the verb is arrive or arriver (infinitive) >> to arriver you must tack on the following endings: ais, ais, ait, ions, iez, aient. the same sentence in the conditionnel becomes  la demoiselle arriverAIT tres tot chaque matin.

The conditionnel in English means  mostly would,  and with the verb pouvoir:could or  with verb devoir : should.

The futur simple means will or shall. It too takes the verb in ts infinitive form and tacks on new endings: ai, as, a, ons, ez, ont. Using the same example: la demoiselle arrive tres ttot chaque matin>> again the verb is arriver , which in the 3rd person singular becomes arriverA.

Exceptions: these verbs are totally irregular and because of that they change their stems; we tack on the same endings as above to conjugate in the ocnditionnel or the futur simple.  The stems are : AVOIR>  aur; ETRE >> ser-; ALLER>> iR-; FAIRE>> fer-, POUVOIR>>pourr-; DEVOIR>> devr-; VOIR>. ver; SAVOIR>>saur-; VENIR, DEVENIR, REVENIR>>> viendr-, deviendr- and reviendr-, PLEUVOIR>. pleuvr-‘ RECEVOIR>> recevr-.