I'm nice because I've grown up being taught this...You treat the people the way you want to be treated.

Half my life I've had rude ass people around me and claimed to be my "friends".
I stayed being a "nice" person.
Being nice is only determined by the one claiming it.
I can say someone is nice but someone else can think differently. Based on their own experience or how they see them as they are.

All my friends out here say I'm the nicest friend they have ever had, and honestly I find that ****ed up that someone like me can be considered the nicest friend but then again...I'm not a complete utter asshole in front of people because that is just stupid.

How to be a nicer person? Question is moot. Anything I can give advise for can make no sense to you. Honestly, you have to figure out how to be nice on your own. You can have help and guidance that can give you an idea on how to be nice...but in the end, you have to find out how.