First rule is to keep memory left on your smartphone
Then, remember to rotate around a virtual axis that is placed between the lens and the sensor; try move around your smartphone, instead of rotate with it.
What @LucioV said. You need to imagine a point in the middle of the lens on your phone and make sure your phone rotates on that point. So you are going around your phone and not your phone going around you. If you move away from the imaginary pivot point you introduce parallax that the stitching software cannot fix.
I have taken about hundreds of photos using Gcam and Street view apps. For me 360 was something that was making me satisfied with places that has views on around. I can remember the days when people used to stare at me taking insane photos with my phone.
Recently I switched to a 360 camera, a cheap one but serves my purpose and I can take decent 360 of places in just one click.