Yes/No questions: да ли and ли-inversion

Да ли is the safest way to ask a yes/no question: place it first, then keep the statement's normal word order unchanged. Да ли говориш српски? (Do you speak Serbian?) is literally Да ли + Говориш српски.

The alternative is ли-inversion: move the verb to the front and attach ли directly after it, in second position, like any other enclitic. Говориш ли српски? asks the same thing. With бити, the long form combines with ли: Јеси ли уморан? (Are you tired?) - see verb-biti-present-a1.

Ли can never stand at the very start of a sentence, and can never attach to a noun or pronoun directly - it always leans on the conjugated verb leading the clause.