Here are the main ways you can get to Montenegro, by airplane, bus, train, car or ferry:
Traveling by airplane: The main Montenegrin airline company is Montenegro Airlines (https://www.montenegroairlines.com) with flies to Podgorica and Tivat from several European destinations. There are two low-cost airline companies available in Montenegro: Wizz Air and Ryan Air.
Traveling by bus: It is very easy to arrive in Montenegro by bus from any of its neighboring countries. All the cities in Montenegro are connected with regular bus lines; check them out here: https://busticket4.me/EN
Traveling by train: Montenegrin railway line connects Bar and Belgrade. As it belongs to European railway network, it is very easy to arrive in Montenegro by train. Check out the railway timetable here: http://www.zcg-prevoz.me/
Traveling by car: Although Montenegro does not have a highway, the motorways are well connected with all the neighboring countries. All of the motorways in Montenegro are free of charge, except the Sozina road tunnel which costs 2.5 euros in one direction, and which connects the capital of Montenegro with the seashore.
Traveling by ferry: If you are in Italy and want to visit Montenegro, you can easily travel by ferry from Bari to Bar. Between April to September, Montenegro Lines (www.montenegrolines.net ) runs between two and six weekly services to Bar from Bari.