How to choose the bpm?

Finding the exact BPM that your track will sound best at can get a bit tricky. Try the following:

1. Quick google search the bpm for your genre (if they give you a range, for instance for DnB it's 160-180, try picking 170 since it sits in the middle).
2. From there, start developing your track. The further your track comes along, the more clear it should become whether it is too fast or too slow. Then you can start fine-tuning your BPM. This becomes much easier when there are vocals involved because the vocals often dictates how fast or slow your track can be. If the BPM goes out of the range of the vocal, the song will start to sound extremely unnatural.
3. Once your track is more developed, you should send your track to an experienced friend that produces, DJs, or who is well-versed with music in general. They can quickly tell you whether it is slightly too fast or too slow. What happens a lot of the times is we grow too accustomed to the way the track sounds because we've listened to our own song hundreds of times. Getting a fresh perspective can help you correct your track by 2 or 3 BPM, which may make all the difference in the presentation your track.

Hope this helps