If you have a good textbook, in the Appendices (at the back) you should have a list of irregular -er verbs.
Regular -er verbs follow the pattern of "parler" = je parle, tu parles, il/elle/on parle, nous parlons, vous parlez, ils/elles parlent
Some irregular -er verbs:
aller = je vais, tu vas, il/elle/on va, nous allons, vous allez, ils/elles vont
envoyer - j'envoie, tu envoies, il/elle/on envoie, nous envoyons, vous envoyez, ils/elles envoient
There are spelling changes in some -er verbs:
1. those ending in -cer, change c to ç before a or o, to keep the soft c sound. (commencer)
2. those ending in -ger, insert a mute e between g and a or o, to keep the soft g sound. (manger)
3. those ending in -yer change y to i before a mute e. (ennuyer)
BUT those ending in -ayer may or may not change (payer = paye OR paie)
4. two verbs with mute e (appeler & jeter), and compounds of those verbs, double the consonant instead of adding the grave accent (j'appelle/je jette)
5. those with é in the syllable before the infinitive ending change é to è only before mute endings (-e, -es, -ent) (espérer)
Just take the "irregular" verbs as you meet them. The spelling only reflects the desired sound!
If and when you need lists of those verbs with spelling changes, just ask! (the "nous" and "vous" forms are close to the infinitive)
Sra (aka Mme)