A previous job I had, involved driving around bus stops and putting stickers on them. When answering I made sure I told them how I worked safely despite being alone (using the relevant equipment). How I managed to keep focused and alert (taking regular breaks, listening to the radio).
A difficult situation I gave was when I was working on the train and had two separate non-fare payers and I had to say what course of action I followed to resolve the situation (called the manager to meet one) and dealt with the other one myself. The guy I dealt with got abusive so I got a coworker to help me to get him to pay.
Use your own examples though, even if you have to 'tweak' them to make yourself look better (that's how I got through). They will keep asking for lots of information so if the situation actually happened to you then all the better as your answers will seem more realistic, than if you try and blag it.
Also remember to emphasise what YOU did. Keep saying I, not we!!