On a standard *nix installation, you could simply use the apachectl script located in the /usr/local/apache/bin directory like this:

/usr/local/apache/bin/apachectl start

It might not be in that specific directory, so you may need to hunt around for it. To do a system-wide search for it, you would do something like this as root:

find / -name apachectl -print

You also might want to make sure that when you start apache, you are logged in as the user you want to run apache. Most people make an account on their system specifically for the web server (like web, www, or apache).