Check to see if the local community college, university or Serbian and Croatian Cultural Center is offering classes. Ask friends if they know of any Serbian and Croatian events you could attend.
Find a tutor who speaks Serbian and Croatian if you can't move to a remote village in Montenegro. There are a number of expats from the former Yugoslavia who live in America, Canada and Australia. Advertise your desire to find a tutor and learn the languages in your local paper, on the community bulletin board and on the Internet.
Set up a study schedule, and mark it in your day planner to remind yourself. Identify benchmarks to aim for as you progress. For example, after six months, you might like to be able to write simple sentences, and after a year, you would like to be able to talk with your aunt from Bosnia when she comes to visit.
Get a good Serbian and Croatian grammar book. Check at the local library, and ask the librarian if she has any recommendations. If you can get a native speaker to go to the bookstore with you, she can help you make an informed choice.
Supplement your print resources with materials from the Internet. Do the online exercises, and keep track of the scores you get on the tests to encourage you to keep studying.
Watch Serbian and Croatian television documentaries. Presenters for documentaries must have good language skills, and you can watch these documentaries until you understand the languages.
Read Serbian and Croatian books. Always have a good book with you, and when you read, say the words aloud so you can hear your pronunciation.
Talk to yourself in the mirror. Pay attention to the way your mouth moves when you speak Serbian and Croatian words.
Listen to Serbian and Croatian music. Download songs and sing along. This is en effective way to learn the rhythm of the language.