In 2006, Dennis Lance wrote a very comprehensive set of tutorials to introduce new users to the art of BVE Route building.
I’ve reproduced them here, with some minor tweaks and some fancy syntax highlighting and tables!
They are divided into several parts, and each part has various sub-sections.

Part 0: Prerequisites

There are a few basic prerequisites for starting this set of tutorials. Please see this page:

Part 1: The Basics

Tutorial 1: Getting started, and laying straight track between two stations.
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-1-first-steps/

Tutorial 2: Adding another station, changing the time, stop points and freeobjects.
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-2-stations-stops-and-the-time/

Tutorial 3: Curves, smooth curves and an adjacant track.
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-3-curves-smooth-curves-an-adjacant-track/

Tutorial 4: Changing the track layout and appearance, and adding run-sounds.
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-4-track-layout-and-textures-run-sounds/

Tutorial 5: Finishing the track layout for our island platform, and adding a double-lead junction. Also, turning on the rain!
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-5-finishing-the-island-platform-and-adding-a-junction-also-turning-on-the-rain/

Tutorial 6: Tidying up the junction, and an introduction to speed limits.
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-6-tidying-the-junction-an-introduction-to-speed-limits/

Part 2: Signalling & Associated

Tutorial 7: More on speed limits, and basic AWS & TPWS
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-7-more-on-speed-limits-and-basic-aws-tpws/

Tutorial 8: Finishing the signalling, AWS & TPWS
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-8-finishing-the-signalling-aws-tpws/

Part 3: Basic Scenery

Tutorial 9: Basic signalling related objects.
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-9-basic-signalling-related-objects/

Tutorial 10: Starting a tunnel
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-10-starting-a-tunnel/

Tutorial 11: Finishing the tunnel and the Brightness command
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-11-finishing-construction-of-the-tunnel-brightness-command/

Tutorial 12: Basic scenery on approach to the tunnel
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-12-scenery-on-approach-to-tunnel/

Tutorial 13: A waterfront & walled walkway on approach to the tunnel
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-13-a-waterfront-and-walled-walkway-on-approach-to-the-tunnel/

Tutorial 14: Finishing the tunnel entrance and introducing lighting (Inbuilt BVE lighting and .X files)
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-14-finishing-the-tunnel-entrance-and-introducing-lighting-built-in-bve-lighting-x-files/

Part 4: The Station

Tutorial 15: Building the island platform
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-15-building-the-island-platform/

Tutorial 16: Platform ramps
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-16-platform-ramps/

Tutorial 17: Building from reference photographs
http://www.bvecornwall.co.uk/wordpress/route-building-tutorial-17-building-from-reference-photographs/