Starting out on an allotment is a lot of work, we were lucky that our plot had already been started by my brother, sister in law and nephews, they'd dug over some of the beds the year before we joined in. Still it was a LOT of work and we threw ourselves right into it. We planned and researched a lot but of course you learn the most from experience as you go along. Planning what was going where was one of my favourite parts of the process. I found that a great way to plan the plot was on my iPad. I drew out the plot in Procreate and have each year's plan on a different layer. It means we can try and stick to some sort of crop rotation plan and remember what was planted where.
I also use my small pocket allotment notebook to take down with me and make notes.