Kazz Hi Kazz, I don't have any diagrams handy, but you could look in a volcanology or perhaps introductory geology book. One problem is that there is no one set of stages that all volcanoes follow when they are erupting.
All volcanic eruptions are different in one way or another, and some are very different.
The only general scheme seems to be that there is an increase in heat and gas reaching the surface prior to the eruption. After that just about anything can happen in any order. Some volcanoes erupt ash first, others lava first, some both.