If you have (or want) to install software not using your distributions package/ports manager you’re left with basically two choices: Install it in /usr/local (i.e. system-wide) or in your homedir (like ~/local). Whatever you decide to do you really should use stow (as i learned today ;). Stow makes managing the different software packages easy. As the dirs under /usr/local get populated (several packages might install different files in ‘lib’ for example) you loose track which package installed what. So when you want to uninstall something its all just a big mess.
Stow avoids this by using symlinks. What you ist install a package into e.g. ~/local/stow/