You must show that you do not have interest in overstaying, show you can afford to travel, not need to work to support you trip.
1 have job that pay a decent wage show funds deposit regularly
2 have resident property under your own name
3 have fat bank account for 6 months and longer.
4 no relatives in the state which can provide shelter and job. BF or GF should show regardless of approve or not, it will enter into evidence when you apply for a fiance or married visa.