Cattitude

I have been quilting for two years. One of my biggest problems is deciding in which direction to press diagonals. For snowballing I have been pressing to the dark however working on a magazine pattern now and it is instructing me to press open. On this particular pattern (Wave Length from AP&Q June 2017) this diagonal seam never meets up with another and therefore no bulk issues. This seems wrong to me, what I am missing? Brings me to my wider question of HST and QST pressing. As a beginner I as choosing to make a lot of simple patterns with these blocks but usually don't need to buy a pattern as they are so basic. Therefore no pressing instructions. I have tried everything and no matter what I do I end up with a lot of bulk when joining blocks and rows.

Any advice? Or could you direct me to a resource, online or otherwise. I have performed quite a few searches including on this site but haven't come up with anything useful.

Thanks!