There's an even easier way. It's called "auto-completion", and it's really handy.
Let's say you're in the folder /Applications and you want to get into the directory called "Microsoft Office X". You could type the whole thing out with the backslashes if you wanted, or you could use gigi's drag-and-drop method. However, it's probably easier if you do this: type the command and then start typing the directory you want to change to (for example, type cd Micros). Now press the tab key. If there's only one folder that starts with the string "Micros", the Terminal will automatically fill in the rest for you, giving you the command cd Microsoft\ Office\ X. Then you can press return and execute the command. If there are two or more folders that start with that string, it'll beep and give you a listing of all those folders that start with that string and then retype what you've already typed. So let's say you have two directories called "Microsoft Office X" and "Microsoft Internet Explorer". If you typed cd Micros and pressed tab, the Terminal would beep, list both Microsoft\ Office\ X and Microsoft\ Internet\ Explorer, and then give you another prompt with cd Micros already typed.
As you can see, this comes in handy very often.
As for your question about partitions, here's your answer. Your partition that OS X is installed on is always going to be the root directory, or simply /. All other partitions are stored in the /Volumes folder. So if lets say the partition you've installed OS X on is called "OSXDisk" and a second partition is called "OtherDisk", then to switch to the "OtherDisk" partition, you would simply type cd /Volumes/OtherDisk and press return. To get back to your main partition that has OS X installed on it, you would simply do cd /.
I hope this helps.