Edinburgh is an explosion of culture in August, when Edinburgh International and Fringe Festivals take over the city. As do the crowds. So if you want Celtic culture and cool, go then. If you want a chilled out capital, go in September when it's all over and the days are still long.
Stalking season is from 1st July to 20th October, with a hind season until 15 February. The Heading for the Scottish Hills website is invaluable for keeping you up to date on what the various estates are doing and when. So if you want to hike in peace, stay away from the stalkers.
Hikers and cyclists will delight at the number of lambs jumping around the fields in April. So Scottish, so sweet. Not worth thinking about, however, if you are vegetarian.
Foodies will love October in Scotland. Seafood is superb from lobster to langoustines, monkfish to mussels. And the game is on, with wild duck, grouse and pheasant very much 'flight to fork'.
Hogmanay or New Year is a countrywide festival with community ceilis, music and whisky flowing throughout the night on 31 December, with a truly Scottish Auld Lang Syne to see you into January.
The midges in Scotland get a lot of bad press, but really they are only an issue at dusk and by the water's edge. And at their worst May until October. Bring nets and Avon Skin So Soft moisturiser (really) and you will be fine. See www. midgeforecast.co.uk for more details.
Scottish tourism is still seasonal in many places, with some hotels and restaurants closing for the winter, usually around late October/November time to around Easter. The Cairngorms National Park and all the skiing facilities an exception of course.
If you want to travel to the Scottish islands between October until March, check the ferry timetables as a lot of them slow down to a stop during months that are out of the traditional tourist season. Similarly they get overcrowded in June, July and August, so book in advance if you can. Some offer standby tickets.