Choosing complementary Primary and Secondary Power Sets is fundamental to creating an effective character. Synergy occurs when your chosen sets enhance each other, covering weaknesses or amplifying strengths. For example, a Blaster with 'Energy Blast' (high damage) and 'Energy Manipulation' (defensive buffs, endurance recovery) creates a more self-sufficient damage dealer. A Scrapper with 'Super Strength' (melee damage) and 'Regeneration' (self-healing, damage resistance) becomes incredibly durable in close combat.
Consider how your chosen sets interact. Do they provide a good balance of offense and defense? Do they offer crowd control if your archetype lacks it? Do they have endurance recovery options? Researching power set combinations and their inherent synergies before committing to a build can save you a lot of respec tokens later on. The official forums and community wikis are excellent resources for exploring popular and effective combinations.