Most of the 3rd group verbs are regular.

partir (to leave)

English	French
I will leave	je partirai
you will leave	tu partiras
he/she will leave	il/elle partira
we will leave	nous partirons
you will leave	vous partirez
they will leave	ils/elles partiront

Some verbs end in "e". Replace it by le futur endings.

prendre (to take)

English	French
I will take	je prendrai
you will take	tu prendras
he/she will take	il/elle prendra
we will take	nous prendrons
you will take	vous prendrez
they will take	ils/elles prendront

Vivre (to live)

English	French
I will live	je vivrai
you will live	tu vivras
he/she will live	il/elle vivra
we will live	nous vivrons
you will live	vous vivrez
they will live	ils/elles vivront

There are however particular cases:

Verbs with "-enir" ending

Replace "-enir" by "-iendr". For example:

venir (to come) >>>> je viendrai

tenir (to hold) >>>> je tiendrai

tenir (to hold)
English	French
I will hold	je tiendrai
you will hold	tu tiendras
he/she will hold	il/elle tiendra
we will hold	nous tiendrons
you will hold	vous tiendrez
they will hold	ils/elles tiendront

verbs with "-rir" endings

Verbs such as mourir (to die) or courir (to run) have a double-r in the future. When saying "je courrai", pronounce "je courrrrrrrai"! ;-)

faire (to do)

No rule, sorry! Just learn...

faire (to do)
English	French
I will do	je ferai
you will do	tu feras
he/she will do	il/elle fera
we will do	nous ferons
you will do	vous ferez
they will do	ils/elles feront

And the others

• voir (to see) >>>> je verrai, tu verras, ...
• verbs as joindre (to join) >>>> je joindrai, tu joindras, ...
• and many many many you'll have to learn !