I did a lot of reading and watching video on YouTube before jumping into straight shaving. It seems that most people advise shaving the right side of your face with your right hand, and left with your left. I had the same difficulty as you with seeing my sideburns. What works for me is the opposite of most advise. I reach across each side. I shave my right side with my left hand, and left with my right. Switch hands and see what works best for you.

Also, I remember someone suggested this video in another post and I've watched it at least 15-20 times. Each time I notice some subtlety or another.

Chimensch's Shaving Video - YouTube