We report on a study of all the large solar energetic particle (SEP) events that occurred during the minimum to maximum interval of solar cycle 23. The main results are: 1. The occurrence rate of the SEP events, long-wavelength type II bursts and the fast and wide frontside western hemispheric CMEs is quite similar, consistent with the scenario that CME-driven shocks accelerate both protons and electrons; major flares have a much higher rate. 2. The SEP intensity is better correlated with the CME speed than with the X-ray flare class. 3. CMEs associated with high-intensity SEPs are about 4 times more likely to be preceded by wide CMEs from the same solar source region, suggesting the importance of the preconditioning of the eruption region. We use a specific event to demonstrate that preceding eruption from a nearby source can significantly affect the properties of SEPs and type II radio bursts.