Handling input confirmations in Linux shell scripting

Question

I'm writing a Linux Shell Script to automate a few things I'm doing on Ubuntu 11.04.

Basically, I'm writing a shell script to install NGINX, MySQL, and PHP, and then configure everything. I know how to do everything via the command-line.

However, I don't know how I'm going to handle the parts where the process asks for user input. For example, certain things I install with apt-get ask you for a confirmation i.e. (Y)es or (N)o.

How exactly would I handle auto-confirmation in the shell script i.e. to automatically confirm Yes or No when asked?