HI, Don't know if I can explain this properly but here goes. When you have two pieces to applique that belong next to each other do you butt them up against each other or should one go a little under the other? If you butt them: where they are butted should there be two lines of stitching, one for each applique or do you stitch the butted part just once and catch both appliques in the stitching? This is for raw edge applique. Are you all scratching your heads on this one?

you can do it either way but each should have it's own stitch line. Look at the design and deside if you think one edge would look better under or beside the other and then stitch away

If you are using a stitch wide enough to catch both pieces of your applique, I would use 1 line of stitching. I'm thinking of a tight zigzag when I say that. What kind of stitch will you be using?

it depends on what you are appliquing...some pieces belong under another- some times the belong side by side- you can stitch them how ever you want- many times when i am machine appliqueing and pieces are side by side (if they are close enough-not with a gap)
i will use a zig-zag or satin stitch that is wide enough to stitch both at once- but if the pieces are different shapes i might stitch each separately---
it depends on what stitch you are using to do your applique-the look you want- and the project itself-
if you are unsure how different ways will look make a practice block that you can try different stitches- design layouts on.

For raw edge, I like to slightly over lap the pieces. If you place them side by side, I would stitch along both edges. :D:D:D

I was thinking of using a blanket stitch and will be doing it by hand since I enjoy that. Thanks for your answer!