The particle よ (YO) is used to give more weight to what is said, encourage someone to do something, emphasize a request.
Isshoni utaimashou yo.
Let’s sing together.
Ashita no kaigi ni okurenaide kudasai yo.
Please don’t be late for the meeting tomorrow.
The particle よ (YO) expresses certainty and self-confidence. If the speaker disagrees with what someone else said, he/she uses よ to denote confidence in his/her own opinion.
Asatte wa shukujitsu da kara byouin wa yasumi desu yo.
The hospital will be closed the day after tomorrow due to the holiday. (even if you think the opposite)
よ (YO) can be used to express annoyance, or even anger.
Kimi no fuku wa hadesugiru yo!
Your clothes are too flashy!
Kenka shicha dame da yo!
Don’t fight! (to kids)
よ (YO) is used to give your interlocutor a piece of information that he/she doesn't have. The speaker believes that the information is important.
Jiko ni atta yo!
I’ve had an accident!
よ (YO) can be used to draw someone's attention to an idea that you want to convey. Therefore, it is normal to find it more often in a conversation.
In some situations, this usage may upset your interlocutor if you don't use it correctly. In fact, it's important to understand that by using it, you put yourself forward. Avoid using it with your boss, for example.