Montenegro-Croatian border crossing

The Montenegro-Croatia border crossing is between the cities of Herceg-Novi on the Montenegro side and near Gruda on the Croatia side. One can walk across this border on foot. The border crossing is fairly primitive and offers no amenities such as an ATM, toilet, or shop.

North towards Dubrovnik
The border crossing from Montenegro to Croatia is on the outskirts of Herceg-Novi. You might find that people are hesitant to drive you over the border. If you find yourself on foot at the crossing, it's approximately 1.2km (moderately uphill) from the border station exiting Montenegro to the border station to enter Croatia.

Once on the Croatia side of the crossing there is a large open area with parking places that you can stand just where all traffic leaving the border post will pass by. It's easy to catch a ride from there. It's likely that, at the very least, you catch one with someone heading to the nearby Dubrovnik airport, where if you're having a slow day, there are multiple buses shuttling arriving passengers to Dubrovnik.

Keep in mind, though that it's much easier done in the morning/early afternoon since traffic gets sparse in the evenings. isin: Balkans

Another good option is get to Lepetane by hitch-hiking or bus (€1.70 from Kotor) and look for a ride the Lepetane-Kamenari ferry, which is free for pedestrians. You can catch the ferry back and forth as many times as you need, and almost all cars that don't have MNE plates are going to Dubrovnik or further along the Croatian coast. This option will save you a lot of time if travelling to Croatia from Kotor.