Craignure

is the usual way to reach Mull, on the Calmac ferry from Oban, which has trains and buses from Glasgow. Ferries sail daily, roughly hourly Apr-Oct and every couple of hours Nov-March, taking 50 mins. Single fares are £3.70 adult, child £1.85, car £13.75, returns are double. Buses and tour coaches meet the ferries at Craignure.
A couple of other car ferry routes link Mull to the Ardnamurchan peninsula: Lochaline to Fishnish, and Kilchoan to Tobermory. You'd only take these to tour remote Ardnamurchan then return via Craignure to the mainland.
By bus: West Coast Motors Bus 95 / 495 runs five times daily between Craignure via Fishnish and Salen to Tobermory (50 mins; no Sunday service Nov-March) - they meet most but not all ferries. Bus 96 / 496 runs four times M-Sat and once on Sunday between Craignure and Fionnphort (for Iona), 70 mins.
West Coast Motors coaches also meet the ferries for tours around Mull and to Iona and other outlying islands.
Craignure is 21 miles from Mull's main settlement of Tobermory. Chris's Taxis (+44 749 3886 237) are based in Tobermory but do pick-ups from the ferry, and other point-to-point journeys and tours around the island.

Mull Car Hire, based next to the pier, is open daily 08:00-20:00, phone +44 1680 812435.
You can walk to Duart Castle but it's 3 miles along narrow roads, you'll be forever dodging traffic.

• Duart Castle

  address: 3 miles south of Craignure
  Dating from 13th C, a stubby fist of a castle ever brandished in the face of central authority, and the seat of Clan MacLean. With cafe and gift shop.
• Torosay Castle & Gardens, a mile south of the pier, are no longer open to the public.

• Craignure Golf Club

  address: Scallastle Bay, Craignure PA65 6AB
  Nine-hole course, visitors welcome.

• Spar

  phone: +44 1680 812301
  address: Craignure, Mull PA65 6AY
  Small supermarket by ferry pier.

• Macgregor's Roadhouse

  phone: +44 1680 812471
  address: Main Street, Craignure PA65 6AW
  Small pub-cum-cafe, handy for the ferry.
• Arlene's Coffee Shop by the pier is open M-Sa 10:00-15:00.

• Craignure Inn

  phone: +44 1680 812305
  address: Craignure PA65 6AZ
  Bar and restaurant in an 18th C drover's inn. The inn is featured in RL Stevenson's novel Kidnapped as the Inn of Torosay. Has rooms, B&B double £100.

• Craignure Bunkhouse

  phone: +44 1680 812043
  address: Craignure PA65 6AZ
  Open all year, 4 dorms & 20 beds with showers and lockers.
• Pennygate Lodge (+44 1680 812333) half a mile south of the ferry pier is a good 3-star, B&B double from £140.

• Shieling HolidaysCampsite with pre-pitched tents (sheilings) and two holiday cottages.

• Isle of Mull Hotel

  phone: +44 1680 812544
  address: Craignure PA65 6BB
  Handy for the ferry terminal but franky shabby and needing an upgrade, with restaurant and bar meals.

• Go northwest on A849 for Tobermory.
• Go southwest on A849 for Bunessan and Fionnphort for the short ferry crossing to Iona.
• Otherwise return to the mainland at Oban.