NOTE: the changes below (from the default ubuntu 8.04 LTS apache2 installation) brought memory usage down from 16MB per apache2 process to about 5MB AND reduced the number of process from 8 (for 1 user with 2 pages open) to 3...
Lower the amount of time the server will wait before failing a request. Timeout 45
prefork [default MPM for Apache 2.0 and 1.3]:
Apache 1.3-based. Multiple processes, 1 thread per process, processes handle requests. Used for security and stability. Has higher memory consumption and lower performance over the newer Apache 2.0-based threaded MPMs.
worker: Apache 2.0-based. Multiple processes, many threads per process, threads handle requests. Used for lower memory consumption and higher performance. Does not provide the same level of isolation request-to-request, as a process-based MPM does.
THESE SETTINGS DEPEND ON INTENDED PERFORMANCE, THIS IS FOR A LOW/MED END LOW UTILIZED SERVER...
MaxClients ? (RAM - size_all_other_processes)/(size_apache_process)
Enable HTTP persistent connections to improve latency times and reduce server load significantly [25% of original load is not uncommon].
prefork MPM: KeepAlive On KeepAliveTimeout 2 MaxKeepAliveRequests 80
worker and winnt MPMs: KeepAlive On KeepAliveTimeout 15 MaxKeepAliveRequests 80
With the prefork MPM, it is recommended to set 'KeepAlive' to 'Off' otherwise a client will tie up an entire process for that span of time.
Usually it's more useful to simply set the 'KeepAliveTimeout' value to something very low [2 seconds seems to be the ideal value]. This is not a problem with the worker MPM [thread-based], or under Windows [which only has the thread-based winnt MPM].
With the worker and winnt MPMs, the default 15 second timeout is setup to keep the connection open for the next page request; to better handle a client going from link to link. Check logs to see how long a client remains on each page before moving on to another link. Set value appropriately [do not set higher than 60 seconds].
Directive MaxRequestsPerChild is used to recycle processes. When this directive is set to 0, an unlimited amount of requests are allowed per process.
Set each "Directory" Directive to AlloOverride None unless you intend on using .htaccess