Whether you are already married or engaged to be married makes a big difference in the green card process. If you are engaged to be married, you must determine whether you want to be married in the United States or in the country where your fiance lives.
If the marriage will take place in the United States, you must request a K-1 visa for your fiance. The benefit of the K-1 visa is that it will allow your fiance to enter the United States, marry within three months of entry, and then complete the paperwork to obtain a green card while your spouse remains in the United States. While the K-1 visa is the fastest way to bring your fiance into the United States, the K-1 visa comes with significantly more work and costs.