How to do a "Y" seam (also known as a set in seam). Edyta Sitar has fabulous instructions with lots of pictures in her book "Scrappy Fireworks Quilts" but she uses them so often I bet she has the same instructions in all her books. There is also a You Tube Video by the Fat Quarter Shop.
https://www.youtube.com/watch?v=qV-LPJpl0JU
So many quilters avoid this very basic technique and it is a shame because it isn't that hard and the more you do the easier they are. So they won't attempt any pattern that calls for it like Lemoyne Star, Lone Star, Tumbling Blocks, Seven Sisters, Bow Tie and so many others. Judy Niemeyer (Quiltworx) uses them quite a bit in her patterns too. You can do the workshop and have everyone assemble a LeMoyne Star (aka 8 pointed star) block or a mini Lone Star Quilt.