• Improve performance (of Adobe After Effects, current version) - Adobe Help Article.  System recommendations, Memory & Multiprocessing preferences, project optimization among other tips.
• FAQ: Optimum memory settings for best performance in After Effects CS4, CS5, CS5.5 -- Adobe Forum post by Todd Kopriva, Sep 18, 2011.
• Memory (RAM) usage in 64-bit After Effects -- Adobe Help Article.

FAQ: What are the optimum memory settings for performance in After Effects? 

(Source: video2brain.com.  See also: the longer version of the above video.)