If you're using IS Boxer, and want a really detailed example on how to set up IWT: http://www.dual-boxing.com/threads/3...469#post312469

Essentially...

Decide on what macro the rogue wants to use.
a) Either a straight castsequence, possibly with a /cast at the end of it (on line 2, as a fall-through).
b) Maybe a two-step macro from sticky threads in the macro forum.
c) Possibly a pseudo-priority system, where many keys are mashed (can weigh this with more keys for abilities you want to fire off more often) and one of them will fire off.

Ensure the rogue has Click to Move enabled.
And that nothing turns it off, within your set up.
Interface Options > Mouse Options > Check the box.
Or On: /console AutoInteract 1
And Off: /console AutoInteract 0

Imbed your IWT key, into your DPS.
You can physically put IWT on '2', with the spammed key on '1'.
And then spam both or just the '1' as desired.
If you're using IS Boxer, I'd integrate it, as per the linked post.
Because that way as a mapped key you can toggle it on and off.

Decide if your rogue will Mutilate/Sinister Strike from any direction.
Or if you'll take the time to get behind the mob for Backstab, or that type of an attack.