Here's another question - do you tie at the seams or in the middle of a fabric piece?

I have a couple that I tied years ago and they are still doing fine even with lots of washing. I tied the one with regular yarn and the other with embroidery thread but I used the entire piece and didn't divide it up.

You don't do it in the seams you just do it in rows across the quilt like a running thread a few inches apart and the go back and cut in the middle of the run and tie.

You may want to consider machine tacking. It is not as difficult to pull the yarn or cotton through the layers and goes quicker. Take a wide , and small lenght ( .05 or 0) stitch inplace ( you can lower your feed dogs), a few times. This can be just as effective as tying, but with out the plyers, and the sometimes larger hole from the larger needle.
PM me if you want me to explain further.

I use to use yarn but it unravels so I use perle cotton or embroidery thread. I buy those big rolls #10 in all colors. Have fun.

I used yarn for my first tied quilt, I won't again as the space between the first and second crease on my finger looks like a mine field!
David

I did a king size plaid quilt with embroidery thread only to have my "surgeons' knots" start coming undone. had to remove all of them and use white yarn. yarn stays.

I tie all my quilts. I use embroidery thread. It comes in several colors. I put them in the corners of the connecting blocks. I put them every other one and I tie a double knot. Use a large eyed needle.

I tie with embroidery floss and use a small or medium curved needle.

I start in the middle of the quilt and then every 4", after that's done, then I offset my ruler 2" vertical and horizontal and then tie again every 4". Most the quilts I've seen that are tied are probably tied every 6"-10", that probably depends on the batting, but regardless if I'm using poly or cotton, I still do it every 4", I like the looks of it better.

I've never had a problem with my knots coming loose.

I use embroidery thread (lots of colors available), all 6 strands, and tie with a square knot.