Bulgarians are predominantly Orthodox Christian; Muslims of Turkish descent make up around nine percent of the population. Social etiquette in Bulgaria is still rather formal. Shaking someone’s hand is the most common form of greeting and you should address someone with their title and surname unless you know them well. It is appropriate to wait for the Bulgarian person to decide when to become less formal with you. When invited to someone’s home it is polite to bring a small gift, and something from your own country will be particularly appreciated.
As for tipping, leaving a ten percent tip will definitely be well received, although it is not obligatory.