I soak the seeds in tepid warm water for about a day. Brugmansia seeds have a corky coat to them so thoroughly soaking them through helps with the germination process.
Plant the seeds in good compost in a propogator tray. Brugmansia seeds require light to germinate so push seeds firmly against the soil without fully covering them. Water immediately after sowing and cover with the propogator lid to keep the humidity high.
You can help the germination success rate by focusing heat via a heat mat at 15c but be careful not to dry them out. Soil should drain well as boggy soil will cause the seed to rot. Keep them in a well lit place. It will take 3 to 4 weeks for angel trumpet seeds to germinate.
Repot the seedling after the forth leaf has come out and move into a larger pot. Keep well watered in a greenhouse or similar. Fertilise in the summer months only. Put fine potting grit at the top of the soil to deter slugs!