Falloir (to be necessary) and valoir (to be worth) are two very common impersonal verbs used in several phrases and situations. Their conjugations are:

Falloir can be translated as must, have to, be required to, etc. It can be followed directly by an infinitive, or a subject and the subjunctive mood.
Il faut rester à la maison aujourd'hui. You must stay at home today.
Il faut pas le faire ! You must not do it!
Il faut qu'il parte à 8h. He must leave at 8.

In addition to worth, valoir mieux is used in translating "it's better."
Ça ne vaut pas la peine. It's not worth it.
Il vaut mieux en rire qu’en pleurer. It's better to laugh about it than cry.