Here are some suggestions for having a memorable experience at Pompeii:
Arriving at Pompeii. To visit Pompeii, you should plan to arrive shortly before the ruins open at 8:30 which means that it is most convenient to stay somewhere nearby. If you are staying elsewhere (such as in Sorrento or Naples), you can either drive to Pompeii and park (there are many parking lots across from the main entrance for about 5 euros a day) or you can take the Circumvesuviana train. It is very easy to hop on the Circumvesuviana train to get to Pompeii from either Sorrento or Naples. There are two Circumvesuviana stations in Pompeii, each serving a different line of the train: (1) If you come to Pompeii from Sorrento or if you take the Sorrento line from Naples, your stop will be the Villa of the Mysteries station (Pompeii Scavi), which is directly across the street from Porta Marina, the main tourist entrance to the archaeological site. (2) If you come from Naples on the Poggiomarino line, your stop will be the Pompeii City station, which is located more in the center of modern Pompeii. In this case, you will walk straight out of the train station until you reach the cathedral square (you can't miss the imposing spire). Then turn right and walk along the main street until you reach the Piazza Anfiteatro, a much quieter entrance to the ruins (my preference). If you are at this entrance when the ruins open, you can avoid the crowds for an hour or so as you explore the eastern ruins.
Entering the ruins. There is only one way to see Pompeii: Arrive shortly before the opening time outside the Piazza Anfiteatro entrance. This is away from most tourist buses (which often arrive at the Porta Marina entrance). When the ticket seller shows up (often after the designated opening time), you will still be one of the few people waiting to enter the ruins. Using the excellent map that's provided free for visitors, you can stroll into the uncrowded southern part of the ruins through the Nucerian Gate. Head for the Garden of the Fugitives and then walk as far east as you can...to the amphitheater and any of the streets along its north side. For the better part of an hour, you may be able to feel as if you are in Pompeii alone.
A slight digression. To make the most of any visit to Pompeii, it is wise to do some reading first. Many people hold a number of misconceptions about the eruption in AD 79 ( there wasn't any lava flow) and the eventual discovery of the ruins. There are no museum-like information placards posted in the ruins, so unless you are knowledgeable about Pompeii, your visit may not be very meaningful (it may just look like one ruined building after another). Here are some suggestions for supplementary reading. And if you are interested in the plaster casts, Bodies from the Ash provides a thorough discussion of the casts, both how they were made, and how archaeologists have deduced information about Pompeian life from them.
Best Books about Pompeii
Getting organized for a visit. These days it costs around €11.00 to see the ruins. Unless you are a member of the EU, there is no discount for seniors or students. Still, a non-EU family of four can visit Pompeii for less than half the price of an adult ticket to many amusement parks...not a bad deal. But once you enter, you cannot leave without paying again (there are no hand stamps). This means that you should be very organized:
1. Bring a large bottle of water (if the day will be warm) and perhaps something to eat. A cafe is located north of the Forum (along with a small bookshop) in case you want to eat in the ruins.
2. Take a guidebook. Even if you have educated yourself about the ruins, a good guidebook is invaluable. Vendors sell them on the way into the ruins, but these are mostly just cheap tourist guides. You would be better served to plan ahead and buy one before you arrive at the site, such as this guidebook. However, even if you forget to bring a guidebook, you will find a good shop at the Porta Marina entrance, which sells a complete range of guidebooks (and various souvenirs) in all major languages.
3. Wear comfortable shoes. The main streets in Pompeii are treacherous with their undulating stones, and I have seen more than one person fall.
4. Plan to go back another day. One visit just whets your appetite for more. If I could, I would visit Pompeii every day--it is that fascinating a place.
5. Bring a good camera, because you will want to take many photos and/or movies. It helps if your camera works well in low light (without a flash) since many rooms are dimly lit. Be prepared for lots of tourists in your shots, unless you arrive early in the morning.
6. Plan for the plaster casts. If you especially want to see the plaster casts, it helps to know more about them ahead of time (since no information is provided in the ruins). You will find a wealth of information about their location in the ruins at this link to the Plaster Casts of Pompeii). You will also find information in Bodies from the Ash and Pompeii's Living Statues: Ancient Roman Lives Stolen from Death.
A Special Ticket: If you wish to visit both Pompeii and Herculaneum, you can buy one ticket (valid for three days) that allows entry to these two sites as well as Oplontis, Stabiae, and Boscoreale (the adult price of about €20.00 is a slight bargain if you plan to visit two sites, but a huge value if you will visit all five; note you can only visit each site once during the three days).
Eating a meal in Pompeii. The ruins offer only one cafe (a branch of the Autogrill chain found on the autostradas in Italy). You will enjoy your food more if you plan to eat outside the site in modern Pompeii, which is filled with tourist restaurants and one McDonalds (between the cathedral and the Piazza Anfiteatro entrance). A beer alternative is a moderately priced restaurant, Carlo Alberti, on a street of the same name, just off the cathedral square. If you are on a budget, there is an adjoining storefront where you can order pizza to go; almost all pizzas were under €5 and worth every penny.
The Grand Tour. If you have made the trip to Pompeii, you should also plan to visit Herculaneum, Mount Vesuvius, and Naples:
If you plan to visit both Pompeii and Herculaneum, you can buy one ticket (valid for three days) that allows entry to these two sites as well as Oplontis, Stabiae, and Boscoreale (the adult price of about €20.00 is a slight bargain if you plan to visit two sites, but a huge value if you will visit all five; note you can only visit each site once during the three days).
To visit Herculaneum, it is probably easiest to take the Circumvesuviana to Ercolano. When you exit the station, walk down the hill, following the main road until it ends at the bottom. The entrance to the site will be sign-posted. Because Herculaneum is much smaller than Pompeii, it is relatively easy to see in half a day (note that there is no food service within the Herculaneum archaeological site itself). It is also much less crowded. As in Pompeii, some buildings will be closed, and many that are open will be in disrepair.
Visiting Mt. Vesuvius
To reach Mt. Vesuvius, you can either drive or catch a bus from Pompeii (near the Porta Marina entrance) or Herculaneum (near the Circumvesuviana station) to Vesuvius. You will want to leave on an early bus (especially if it is a hot day) and take a good supply of water. The bus will deliver you to the Vesuvius parking lot (about halfway up the volcano). From there, you can climb to the top and (after paying a small fee) even walk along the rim of the crater. If it is a clear day, you can see to Pompeii and beyond. Even on a foggy or hazy day, it is still worth a visit.
To complete your tour of Pompeii, plan to visit the National Archaeological Museum (Museo Archeologico Nazionale) in Naples. If you take the Circumvesuviana into Naples (and have purchased a one-day travel pass), you can use the Naples underground all day as well. Head for the Cavour station, which is the museum's stop. It is best to visit the museum after Pompeii, since you will be amazed (having seen the ruined buildings) at what was salvaged from them. The museum's Pompeii exhibits are breathtaking and include frescoes, statues, ornamental objects, and everyday items. It is simply not to be missed (closed Tuesdays).