letter curriculum What do you use

Or how do you teach letters . I used to teacher letter through out my themes . Then i taught them they way you learn to write them But i found that a little hard for some of my young 2 to 5 year olds . Then last year i change to letter Thursday . where worked well but i find a little flat and not sure the best . So how do you teach letters to your preschoolers and what Curriculum do you use if use one ? thanks ! planning for Sept already