In French, there are some verbs that are conjugated almost like good old regular verbs, but with some slight alterations. I want to talk about two major types of "almost-regular" verbs: (1) the -eCer verbs and the (2) -cer/-ger verbs.
1. -eCer verbs
This type of verb has an infinitive form that ends in "e," plus a single consonant, plus "er." Examples:
s'appeler (to be named/called)
jeter (to throw)
amener (to bring)
péter (to burst, fart)
se promener (to walk/go walking)
Watch how each of the above verbs behaves when each is conjugated in the present indicative (l'indicatif du présent):
nous nous appelons
vous vous appelez
je me promène
tu te promènes
il se promène
nous nous promenons
vous vous promenez
ils se promènent
Notice anything in common about the ways in which the above verbs "twist" themselves away from the regular "-er" form? Perhaps the first thing to note is that the first, second, and third-person singular conjugations are all spelled differently from the infinitive: s'appeler gets a double "l"; jeter gets a double "t"; amener gets a grave accent (un accent grave); péter does, too; and so does se promener. There's no rule governing what -eCer verb gets which type of conjugation; as with all irregular verbs, these "almost-regular" verbs will simply need to be memorized.
Note, too, that the first- and second-person plural forms (nous et vous) are conjugated normally, i.e., in the manner of regular "-er" verbs. Finally, note that the third-person plural forms (ils, elles) go back to being slightly irregular.
Keep this irregularity in mind whenever you see any -eCer verbs.
2. -cer/-ger verbs
This type of "-er" verb ends in -cer or -ger. Examples:
lancer (to throw, launch)
annoncer (to announce)
commencer (to begin, start, commence)
manger (to eat)
plonger (to dive, plunge)
voyager (to travel)
Watch what happens when we conjugate the "-cer" verbs.
And now, the "-ger" verbs:
What rule do you see at work here? In truth, the rule is as much about pronunciation as it is about conjugation: in French, it's often the case that the pronunciation of the letters "c" and "g" will change in front of the vowels "a" and "o." This rule operates in nouns just as it does in verbs:
le français (not le francais)
So you have to understand that, if you want your "c" to sound like an "s" in front of "a" and "o," you need to add the cedilla (la cédille), that little diacritical mark that dangles under the "c." If you forget the cedilla and mistakenly write "le francais," a Frenchman will read that and mentally hear "le franké." Not pleasant.
For a "g" to be a soft "g" in front of "a" and "o," you need to add an "e." Hence: nous voyageons.
As with any language, French is full of irregularities. These can drive a beginning student crazy, but it's best to learn them well now; otherwise, you may form bad habits in your writing and speech later on. Strive for perfection as you learn the language so that you don't doom yourself to speaking it with a laughable accent. Bad habits, once formed, are very hard to unlearn.