I hope I can help. I copied and pasted my email to Phylhl and edited it to post here. Now remember, I'd never tiled before when I did this. It has been 2 years almost since I put this in. I may have forgotten some of the details.

Lets see. I determined my center starting point on each wall and did the first tile at the counter on end at 45 degrees. Then proceeded from there to each side working across and up. The center of the tile layout is a zigg-zagg line and the center is through that. Does that make sense? If the wall is centered the trimmed ends will look that same at both ends. As I explain below, I didn't center my tile to the center of the wall, but to the larger features in the area, like the stove or the window. I think this picture is telling that it was a first time tiler installing this. The edges of the cuts are not filed smooth like I started doing at the end of the job at the last few counter areas on the other wall. Oh well.

I lucked out on my sink area pictured above, because I centered the zigzag line at the faucet instead of the center of the wall.

You may not want to center the wall but center on a feature like I did on my faucet. I also did the centering on my stove wall by centering the stove/cabinet, lucked out again as the ends look ok. Note that the right and left are different. It can be a problem if you end up with tiny slivers. For me I can deal with it but I am not a professional and have the time to manipulate the tiny pieces and use my imagination and think "these are so
cute". I don't think professionals do that :)

Also see how the center is averaged between the 2 sides of the herringbone tile, at the cabinet centerline.

I didn't concern myself with how these 2x4 ended at the cabinet bottoms (underneath), because I can't see them. But It may be something to consider with your cabinets.

Now the hard part for me was keeping that 45Degree work true. I used several drafting triangles and would tape them in place to brace my work while it dried.

Here is an example of getting out of 45 when I tried to straighten my vertical direction. It multiplied the error with each row. See how some spaces are larger than the others, that is the error I was getting.

I ended up taking the entire area down and starting again. It hadn't dried yet. I was also using mastic as that was what was recommended by the tile shop where I bought the tile. I didn't know about Mongo and Bill V. yet. I found it easy to use and it is in a non wet area, for the most part. I do worry about the sink area though. If I ever put a backsplash in again I would use thinset. But so far it has been fine.

I used LOTS of the spacers, 4 for each side as each long side touches 2 tiles and I thought that was important that each tile had 2 spacers. There are errors in my wall but over all I think it turned out fairly well and it
is very pretty with my cabinets.

And don't freak when you see this, like I did:

Because it dried to this: