Use them together, in this order. Equivalence partitioning groups inputs the system should treat the same, and one test per partition is enough. Boundary value analysis then tests the edges of ordered partitions, because developers often misplace or omit boundaries, for example writing > 18 where >= 18 was meant. ISTQB's current syllabus covers 2-value boundary analysis (the boundary and its nearest neighbor outside the partition) and 3-value (also the value on the other side). Decision tables capture combinations of business-rule conditions and their outcomes, and state transition testing suits workflows. A good test case states its preconditions, one action sequence, and a specific expected result taken from a requirement.

Sources: ISTQB black-box techniques, ISTQB guide on the three techniques, QASkills guide