How do I find a good PR company

The best thing to do with PR is to find a good PR person/company who knows and works with your genre, our PR person may not do you any good as they may specialize in a totally different genre.
Every PR company and genre has its own set of specific contacts, ezines, magazines, radio stations, etc, etc to blast to, which is another reason why it is so important to get your genre and niche figured out. You don't want to waste money on PR blasting into a community that does not relate to or engage with your genre.

What you can do is go onto Facebook and find other bands you know of in your genre. If you can find some independent artists in your genre who are more well known, that is even better. Check out their "about" section and you should find a list of contacts etc, one of which will be their PR contact. These are valuable because they have already been vetted. Make a list of them and reach out. Send an email with a short bio introducing yourself and your music, any press you may have had or accomplishments and ask them if they would be willing to work with you.

So, basically, you need to do your research...Success is based 95% on research and 5% on implementation. That is a good rule of thumb to keep in mind throughout everything you do as a musician and artistpreneur.