I alternate my starting point on the strips like Piney and can vouch for this method to keep strips straight.

I alternate the starting end when sewing strips as well... did a class for a bargello quilt and that is what the tutor taught us...

Patrice... the quilt top is now at the quilters.... I finally made it !!!

You need to make sure that your strips are straight when you cut them. If you have the dreaded V in them they won't lay straight and will be wavy when sewing. And you should aways press not iron your strips. Ironing can pull them out of shape. Debbie

One can avoid the dreaded "V" if the fold of the fabric is straight along a line on your ruler. Obviously, if there are two folds BOTH must be align straight on a line. You may need to giggle the fabric to get them both on parallel lines, but no "V's".

Suzanne

If you are sewing a panel of several strips, assemble them in pairs first and then join the pairs to make sets of four and then assemble those... instead of starting with one strip and continuing to add to it. You want to handle the fabric as little as possible.

And probably, you are pulling on the strips as you sew. It's hard to NOT do that, when you have long skinny strips to sew together!