Do you have a specific reason for wanting to set a static IP address? it's not needed in the vast majority of situations. If you do need it, it should be either by request from a network administrator at your organization (in which case it's his responsibility to assist you and provide the proper config values), or because you know you need it on a network you built.

-First of all, when I run ifconfig, I find that both lo and wlan0 have downloaded packets. In my /etc/network/interfaces file it says auto
lo. Which should I be setting?

lo is an internal loopback interface. You don't need to change this one. Read about the loopback interface here:

http://en.wikipedia.org/wiki/Loopback

-Secondly, every guide I've found does it as though eth0 is the main connection, but it isn't for me? So what should I be doing
differently?

What is your main connection? If it's eth1, you should apply the instructions from your guides to eth1 instead. Use common sense here :) It would help if you could tell us which guides you're looking at.

-Next: If I do it the graphical way, through Network settings, do I need to change the settings for both IPV4 and IPV6? Every guide I've
found has only ever done it for IVP4.

Not unless you know you need IPV6. This would be something your network administrator can tell you. If it's your own network, you should know whether you have configured or need IPV6.

-Lastly, how do I know what to set my ip address as when I set it to static?

Ah, here's the crux of the matter. You should know this, either because your network administrator told you "configure a static IP on your machine, here are the config parameters") or because you decided "I'll make my home network fully static, here's how I'm going to allocate my address space, here's the IP address for the gateway, this is the IP for my computer" and so on.

If you don't really know what IP address to set, then potentially you don't really need to set one.

I suggest you read up on what setting up a private network with static addresses entails (http://www.wikihow.com/Set-up-a-Private-Network), you don't need to follow the instructions but it will help you understand how to plan a small network and determine whether you want/need to do this.