The futur simple is, indeed, a fairly simple tense. Unlike the present tense, the endings (la terminaison) always remain the same, regardless of whether the verb is regular or irregular. The root or stem (le radical) of the verb is also, always constant but can look quite different from the root of the same verb in a different tense. This is of course, especially true for irregular verbs.
Regular verbs are super easy in the future simple.
Regular ER verbs and IR verbs use the whole infinitive verb as the root or stem (le radical).
Regular RE verbs drop the last ‘e’ of their infinitive to form the root.
The endings (les terminaisons) are also quite basic. You should recognize the endings for je, tu, il/elle and ils/elles as being the verb avoir. Nous and vous have the same endings in the future simple as they do for the present tense.
Here is a table of regular verbs conjugated in the future simple:
Irregular verbs are fairly easy too, if you know the root. Remember, the root does not change once it has been established and the endings are the same as the regular verbs. Here is a chart with some of the most used irregular verbs.