Scotland is on an island, so simply driving there overland isn’t an option. How to travel to Scotland with or without a car, and what to watch out for – it’s all here.

Getting there by …
… plane (currently only available in German)
… ferry
… train (currently only available in German)
There’s basically one decision to make right at the start: do you want to drive your own car in Scotland, or not? If you want to bring a motorhome, say, the only options are the Eurotunnel or the ferries. So that choice gets settled pretty quickly. Whether to bring your own car should also depend on how comfortable you are with driving in Scotland (currently only available in German) – the keyword being: driving on the left.
You have more freedom getting there if you plan to get around Scotland by rental car or public transport. In that case, flying is the first choice. It’s fast, comfortable, and usually the cheapest option.
I’ve only included getting there by train because the question does come up fairly often. For someone with plenty of time who enjoys watching the scenery go by, the rail link to Scotland is certainly an alternative. For everyone else who wants to spend most of their time actually in the Highlands, though, it’s not really a solution.
Personal note: I always fly as close to the Highlands as possible and pick up a rental car once there. That way I can get around more easily and reach my destination quickly. I’ve flown into Aberdeen, Edinburgh and Glasgow before. In summer 2013 it was off to Inverness.
Travel formalities: Which passport is valid?
Since Brexit, EU citizens must present a valid passport. A national ID card is no longer accepted. In addition, electronic entry applications, the ETAs, now have to be submitted. All the formalities for entering Scotland can be found here (currently only available in German).
Pets: Can the dog come along?
In the past, all animals entering the UK first had to spend six months in quarantine. That’s changed since 2000.

Nowadays (as of 2015) the animal must have a registered microchip implanted. After implantation, the animal must have been vaccinated against rabies at least 21 days before travel. It must also have been treated against tapeworm and ticks no earlier than 120 hours and no later than 24 hours before travel.
In addition, as of this year an EU pet passport must also be carried for travel within the EU. It must include veterinary confirmation that the animal has valid protection against rabies. Without it – no entry.
In addition, no more than five animals may be brought in. Exceptions to this number are only allowed if it’s for a sporting event and no change of ownership is planned. Proof of participation in the sporting event must be shown for this.
You can read the detailed rules, in English, from the Department for Environment, Food & Rural Affairs.