Here's what I found works for me....check the quarter in. measurement from needle to seam. Done! Next, I began using Aurofil thread. It's visibly thinner than the old Coats and Clark and Mettler 50 wt.. That change alone made a tremendous difference. But, the coup d'etat on precision came from two things. Sister Marie Clare told us (40 years ago) that our iron was the most important tool we had when sewing. I believed her and I make sure everything is pressed properly open, etc. And then (drum roll.....) the ever popular Elmers School Glue. A drop on the nested seam, NO iron necessary. Just press closed with fingers and sew. BINGO! perfect points. If gluing a row of blocks together, I hit each seam with Elmers, pinch together and place a pin somewhere to hold the place until ready to sew. I then proceed to the next block. I cannot tell you what doing the above has meant for reduction of eye twitches when I look at my work. I'd say 98% of all my seams are breathlessly perfect. The other 2% were usually gross piecer error and I need to stay humble so I rip. Hope you try these things and live happily ever after!