It could be your machine settings... Does your machine have a way to adjust the pressure on your presser foot? You might need more or less pressure.

I don't mark anything, usually. It helps to sew really fast to keep the lines straight, especially if there is nothing to 'follow', such as in stitch-in-the-ditch. I always use a walking foot for my straight line quilting, so I don't have to fight the layers shifting.

I starch my fabric a little. I use the painter's tape and I also have the 1/4" tape. To be consistent I mark a "v" directed to the side I'm going to stitch. I quit throwing my starched fabric into the dryer. It was causing a build up and I don't need a fire. I use my ironing board which is adjustable and my extra wide board to help hold my fabric up so no drag. Just pull the ironing board up to the side of the sewing cabinet. I have round quilt clips that help hold the fabric in place. Works for me!

If your using a domestic sewing machine, I use my walking foot. It has the bars on it, and you only need to mark that first line.

I mark straight lines first. I mark all crosshatching then use a ruler to follow the straight lines. Works for me.

I'm in the middle of taking a Craftsy class from Cindy Needham. She says with straight lines it is ok to be inconsistent--if you are consistently inconsistent it creates interest. And her work does look good. Of course this only works in smaller spaces, I think.

This class is the best thing I've done in quilting. Repeating lessons, going back to find out if she 'really said that' any time I want. One class and I'm sold on Craftsy AND Cindy Needham.

I mark my crosshatching with painter's tape or a Hera marker by Clover (sold in JAF). You always want to mark your center seam so you always refer to it to keep your lines straight.