Truro is a small cathedral city (population 22,000) in the Duchy of Cornwall, of which it is the administrative capital.
The Cornish will insist this is a city. Anyone from outside of Cornwall will have visions of a built-up centre with a large conurbation and a good public transport system: don't. Truro is a practical city once you're in, and residents of other Cornish Towns will often visit to shop with more variety. But, unless you're staying within walking distance of the centre, expect to either drive in or have to plan a journey. There is a very small 'inner-city' area surrounding the centre. Even the most immediate 'suburbs' are small villages that have nothing but a few miles of field and a winding road separating them from the centre.
Trains from London Paddington - Plymouth - Truro, & Bristol - Plymouth - Truro
Truro is at the junction of the A39 and A390 arterial roads, some 14 miles north of Falmouth.
Coaches from various parts of the UK call at Truro; you may have to change at Plymouth, via a seriously grotty & unwelcoming bus station.
Buses from Truro go to numerous Cornish towns & villages (timetables available online from First & Western Greyhound). Visitors be warned: for some unfathomable reason, the Information Office in the main bus station in Truro is closed all weekend - just when holidaymakers might want to use it!
There is a good Park & Ride car park to the west of Truro, at Threemilestone, with frequent shuttle buses into the city centre which also call at the rail station. Parking in the city centre is expensive and limited, especially during the summer, although the largish Tesco's on the ring road allows 2 hours free parking for customers (NB: as of 2013 this is auto-camera controlled and you must enter a code from your till receipt to avoid being fined).
Royal Cornwall Museum, River Street, open Mo-Sa 10am-5pm, last admission 4.30pm, tel 01872 272205, free admission - includes the Courtney Library and exhibitions devoted to the history, culture and geography of Cornwall. 2013 - sadly, the Museum no longer offers free entry.
Have High Tea at Charlotte's - In a Victorian building on the main shopping square in Truro, Charlotte's, on the second floor, is a step back in time. The tea is Cornish grown as well!!!.
Attend a performance at The Hall for Cornwall- a wide variety of music, theatre, and dance productions rotate through the Hall for Cornwall continually. Its a regular stop for National Theatre productions. In downtown Truro, the signs are easy to spot.
Watch a film at The Plaza - Courtesy of WTW Cinemas, opened in 1938 and now with four screens 
Take the river ferry down to Falmouth - calling in at Trelissick (NT garden) en route - if you're lucky you might see seals on your way downstream.
Try the River Walk to Tresillian - take the Malpas Road (just before Radio Cornwall on the A39 roundabout) and walk along the river's edge for several miles. Stop for a drink at The Heron in Malpas & look over the river to the heronry on the far bank, then continue past cottages and fields until the path reaches the main road near the peaceful hamlet of St Clement. Continue through Tresillian to The Wheel Inn, just before Tresillian Bridge, the site of one of the last battles of the Civil War. Catch the bus back to Truro.
Good number of shops including a rather large Marks and Spencers.
There are two covered markets: one leads off the Piazza (outside M&S) -several small traditional stalls. The other leads off Lemon St (near the cinema) - the little shops here would appeal more to the eco/organic minded, and there's a pleasant coffee shop cum art gallery upstairs where you can usually find a seat.
On Saturday mornings there's a great Farmers' Market on the Piazza - good local produce, including delicious Cornish ducks, cheeses, bread, rose veal, plants to take home… Wednesday's market in the same place is smaller.
Pippa's - Steakhouse, fantastic food at reasonable prices, child friendly and lovely atmosphere
Cornish pasty: bakeries include W.C. Rowe's on Victoria Square and Lemon Quay, Oggy Oggy on River Street, and Warrens on New Bridge Street and the cathedral square. W.C. Rowes is most popular.
Saffron buns. Delicious sweet fruit buns flavoured with saffron, from the bakers above. Also "tea treats" (bigger than a bun) and saffron cake, like a fruit loaf, to be sliced, and sometimes toasted & buttered.
First Devon & Cornwall number 14 & 18 busses run up to every fifteen minutes (this is very good for anywhere in Cornwall, even central Truro); destinations include Truro Railway Station, Camborne, and Redruth, and can be caught at the bus station on Lemon Quay or Victoria Square.
Truro Railway Station is a short but hilly walk from the centre. Trains run hourly between Penzance and Plymouth with services to/from London every 2 hours.