probibly best plugging your guitar into the pod, and from the pod, into your amp if you are using the tones from the pod

watch this video of a guy doing just that - it will give you tips and tricks to get the best sound out of it.

http://www.youtube.com/watch?v=HdLwjijmPW8

A very good video, probibly the best, most in depth video about the pod X3 live on youtube so far. It is a full review, but part 4 is the tonal tips and tricks, including sound examples.

However, if you want to just use the effects, and not taint your tones in the amp, use a Boss LS-2 line selecter to get you a good bypass tone, because the pod kinda messes up the bypass tone.

This link will lead you to a thread about making the pod x3 live bypass

http://line6.com/community/thread/20096?tstart=0

Although you have the XT, the same rules apply

Hope that helps