Multiple or cluster There are two basic types of arrangements when it comes to incorporating a number of pendant lights in the same area. You can go for a cluster, a sort of tight mix of several pendants usually hanging from the same spot, or you could also just spread out pendants hanging from different points on the ceiling for an effect.
Multiple lights means the power to manipulate the feel of the space Place the fixtures close together and you have a energetic bundle of decor that will infuse a space with energy. Spread multiple fixtures out and they'll elicit a more calming and relaxing feel on the space.
Height plays a huge part Hang them all at the same height and distance and your space will feel clean, crisp and in control. Hung at different heights and at random distances and you'll project an exciting, unexpected feel to a room. Explore the idea of placing randomly-hung pendants in a really stark, modern space and perfectly aligned pendants in a really casual space to see the contrast that can be created.
Uniform versus random If you get the exact same light fixture and repeat it several times, it'll project a powerful modern aesthetic with a strong feeling of harmony. Decide to incorporate different shapes or light fixtures in one grouping and you'll give off a more casual, bohemian feeling. Consider the same rule with different kinds of lights as you might implement with different kinds of dining room chairs around a table: find something for each to have in common to connect them all aesthetically (like color, size or material).
MORE MULTIPLE PENDANT INSPIRATION ON APARTMENT THERAPY:
• Small Space Lighting Solution: Multiple Pendant Lamps
• Good Questions: At What Height Should a Pendant Hang Above a Table?
• Roundup: Pendant Lamps Without Hard Wiring
• Kathleen Hills: Cluster Pendant Lights
(Images -- 1: Etsy; 2: West Elm; 3:My Deco Blog; 4: Etsy; 5: Knack Studios; 6: IKEA 2012 Preview: Stylists' Design Ideas Worth Stealing; 7: Webber + Studio, Architects via Houzz.com; 8: Victorian Mini Pendant Lights by Wilmette Lighting via The Lighting Blog; 9: Fresh Home via Nemm Design + Lifestyle; 10: Kitchen Renovations: Best Decisions & Biggest Regrets)