Wikivoyage uses separate phrasebooks for Serbian, Croatian, Bosnian and Montenegrin, to help travellers avoid mistakes based on regional differences. The differences, in both vocabulary and accents, are very few, and any of the following phrasebooks can be used wherever you may go.
The other South Slavic languages (Slovenian, Macedonian and Bulgarian) are also close to Serbo-Croatian. People from areas of Croatia bordering Slovenia usually have no trouble understanding Slovenian, while those who live in southeastern Serbia understand Macedonian and Bulgarian without much difficulty.