After having used an iPhone for several years, I expect a certain level of performance from a cell phone operating system. The Android OS, while wide open and easily customizable, needs help when it comes to memory management. One of the same items that many Android users tout as an advantage actually works against the operating system. Background tasks are poorly handled in the Android OS. Not to go into details, but most apps do not need to be kept in memory if not in the foreground or actively working, e.g. playing music or supplying GPS directions.
For this reason, I highly recommend using Droid Mate’s Smart Memory Booster Pro. This app helps the OS clean up messes by looking for applications not currently in play and cleaning them from memory. This process can be customized in several ways, including at time intervals, when the screen locks, and when memory dwindles past a certain level. They, also, offer a regular version version which does not offer as many automated processes, but which can be used manually and when the screen locks to clean memory. For the $2, it is well worth buying the pro version.
*Full disclosure: I have no affiliation with Droid Mate and only offer this as a recommendation that is based on much experimentation on my part.