Depends on your app, but... Split static content serving from dynamic. Can start off on same server but requirements for each are so different it pays to have

Depends on your app, but... Split static content serving from dynamic. Can start off on same server but requirements for each are so different it pays to have tuned processes serving each. Build customized, svelt apache or use nginx. Get separate DB server, get lots mem for DB server, tune DB to use that memory. Few/None are setup up out of box to use 4-8GB+ well. Get more mem for http box(es), use memcache/similar to take advantage of that memory.