We did a Scotland trip last summer, and it was excellent! Before we left I asked a Scottish acquaintance for suggestions about driving around the country, and here is his very detailed response (he wrote it with the idea that we'd fly into and out of Edinburgh):
Start from Edinburgh. You will probably do most driving in the forenoons...... the sun will be behind you most of the way, if you start from Edinburgh!
Why not Glasgow? Edinburgh is a historic and cultural city. Glasgow is nowadays a modern up to date city Edinburgh has many unique sights.
Head north on the M90 and cross the Forth Road bridge. You will see one of the wonders of Scottish bridge building on your right hand side - The Forth Rail bridge with its great cantilever structure.
Once over the bridge follow the M90 to just past Kinross
Branch off on the A91 and make a detour to my home town, St. Andrews - ONLY IF YOU ARE INTERESTED IN GOLF.
otherwise:
After crossing the bridge take the A91 at Kinross and head west past Dollar You will pass some places with Rob Roy history.
Continue to Stirling. Here is Braveheart country. A monument to him and the bridge where he smashed the english. Also the site of the 1314 Battle of Bannockburn where my forefather , King Robert The Bruce thrashed the english!!!
Also Stirling Castle.
Head north, getting on the A94.... more Rob Roy country.
Head north past Lochearnhead. At the T junction a short detour to the east on the A827 takes you to Killin... nice views.
Return along the A827 and continue west A85, to Crianlarach, branch north on the A82, past Tyndrum, over the hilss and into Glen Coe. Very impressive peaks and dark history around the Massacre of Glencoe!
Arriving at the Caledonia canal...pass North Ballachulish and up to Fort William.
Head West on the A830 and at Glenfinnan see the railway viaduct made famous in the Harry Potter movies and at the same place the Glenfinnan monument to Bonnie Prince Charlie....
Follow the A830 to the end of the road at Mallaig and take the ferry to The Isle of Skye. Impressive peaks loved by climbers.
A 851 in Skye, then right on the A87 and over the hated modern bridge to the mainland again.
Head east on the A87... then the A887 until you are back at the Caledonian canal and Invermoriston.
Going north on the A82 with Loch Ness on your right.
Stop at Urquhart Castle and you have a very nice Visitor centre and the castle. From here sightings of Nessie are most common.
Back on the road north again.
Drumnadrochit has a Nessie centre with and interesting presentation on the history of Nessie.
Headin north again to Inverness.
The highlands to the north of the Caledonian canal tend to get boring..... so I wouldn't suggest going further up than Inverness.
best and quickest route back to Edinburgh is the A9.
But slow down when you get to Aviemore.
There are a lot of whisky ditilleries there famous for their single malts! Also the Cairngorm Whisky Centre.....
Down at perth you leave the Highlands....... and get onto the M90 and back over the Forth bridge and to Edinburgh.