I remember the month before my little one started Kindergarten, we made a paper chain to count down the days. He had been in a preschool & daycare type setting before but for whatever reason, Kindergarten was this huge new exciting adventure! He couldn't wait (and let's be honest, I couldn't wait as well). He was my first kiddo to begin Kindergarten so in a sense, we both were walking into the big unknown.
When I am starting new adventures, I prefer to have an idea for what I am stepping into. I like to be pretty informed so that I can shepherd my kiddo through the experience as well. So when we were getting ready for kinder, I asked my friends (who had already done the transition) as many questions as I could. I also got a few books to start reading with my kiddo.
Here is a link to a few options for books that help children as they transition to kindergarten.
About a month before, we started talking a lot about kindergarten. We would walk by the school and play at the playground on the weekend when it was open to the public. We read books before bed and drew pictures of what we thought his teacher might look like. We practiced letters and numbers. We talked through how we interact with other friends at school. I had a short mental list of things I wanted to prepare him about and I just worked through it as the opportunities became available.
A final tip: if you are a mama with other little ones, it can be helpful to find out when the kindergarten orientation is taking place. You can hopefully find a sitter for that meeting and maybe even for the first day of school! I found it really helpful to be able to give my kiddo my full attention during those times when he was feeling anxious.