Most people hardly ever get flashbacks. Anyway flashbacks are not something that are caused by the drug itself. Flashbacks are caused by experiences so intense that your mind can't begin to comprehend them. You know, like war veterans getting flashbacks of the war, without ever taking any sort of psychedelic drug.
LSD is one of the safest substances ever developed by man. If you use it responsibly that is.
However: be prepared for your world view to be permanently altered. After your first trip you will never be the same, there's no going back to ignorance. This is usually a positive thing though.