I first practiced with Funaki sensei who immediately picked up on my continual problem of weak seme and not relaxing my arms/shoulders. He also told me not to move backwards (I seem to do this more when I visit an unfamiliar dojo... must be the nerves). I performed a number of shomen cuts with seme and relaxed posture which gained approval. Why cant I do this all the time?
He also told me to concentrate intently, focusing on my opponents's eyes but viewing the whole body (The whole mountain).
I think i'll acknowledge seme and tense arms as a long term issue as it's pointless me repeating the same kind of post all the time. Coincidentally, the BKA recently posted a good article on Seme and Tame here, an article by Kenshi247 is here. A poster on KendoWorld forum submitted an interesting seme vid here.
I also practiced with Holt sensei who taught me improved zanshin. I tend to run though too far after a men cut so sensei explained I need only to run slightly over two shinai distances away (mine + my opponents). In addition, I need to keep my hands up and shinai forward during the run though and as I rotate to face my aite, not pull them into my chest like i'm doing now. This will stop people creeping up behind me and cutting as I turn.
Holt sensei's final point for better zashin is to turn the correct way to face my aite. If they are behind and to the left then turn anti-clockwaise, behind right then turn clockwise to face them.