I am very lucky when it comes to my main supervisor. He is in the lab most days and is fine with us just walking into his office and asking for a chat, or we just talk over morning tea - usually for quick questions we have about methods or problems. He is very busy, but he always makes time. Long meetings are about monthly and we get a couple of days notice to prepare results and lab books etc.
In my first year I hated meetings. Lots of failed experiments meant I never had any results and it was awful to talk about my work. One day, he came looking for me for a meeting, and I hid under my desk from him! He was very good and just laughed as he pulled me out. Looking back, I now realise how patient he was.