Larger baskets for one thing, but the real difference is usually feed and water, though conditions make a difference too - a basket in half sun half shade does better than one in full sun. Feed should be something with an NPK of 6-6-6 (Miracle Gro liquid General Purpose is the closest I've found), watering should be night and morning in hot dry weather, and feed every 3/5 days.

Mine are in 16" baskets I pinch out the first leader and feed every 2 weeks, water every evening and dead head most days. The great thing is not to knock into them and avoid them just dropping straight over so I plant lobelia trailer in the underside of the basket and this seems to support the heavy trails.