Linux etc.

The file you need to edit is /boot/grub/menu.lst and it contains lots of helpful comments. The two lines you’ll most likely need are:
timeout 10
which gives the timeout in seconds, and
default 0
which defines the default boot option, as the order of the item in the menu list, [...]

The latest (4.0) version of apacite no longer conflicts with the
package hyperref, but you must load hyperref before
apacite.
That is, the preamble of your document should look something like this:
\documentclass{article}
… other packages etc …
\usepackage{hyperref}
\usepackage{apacite}
\begin{document}
…
At least, that is the only way it worked for me. When I had apacite
loaded first, LaTeX would hang on the second [...]