Trying to decide when and where from to go to Mt Vesuvius can be a bit tricky. If you decide to go by train, it can take a while. And there are tours that tend to combine Mt Vesuvius with Pompeii for example.
I don’t recommend doing these tours, and instead you can go to Mt Vesuvius on your own by catching a bus from Pompeii. In this instance, I decided to go at 3pm which meant that the sun was not at its highest and it gave me a chance to rest after spending almost half an Italian summer’s day in Pompeii.
Once you arrive, you are taken near the base. You then buy a ticket at the entrance or the bus driver offers it (they do not markup the price). And from there, you proceed to walk.
Most people were appropriately dressed but I even saw some people wear wedges or bowler shoes. Not recommended! You can take your time going up the mountain. There are a few ‘stations’ offering things from souvenirs to water and even alcoholic drinks.
Once you reach the rim of the volcano you have the option to walk around it, then come back and walk down the mountain.
You can read posts about Pompeii below: