Len, not hard at all, and if you're realiable and don't give people too much problems, they may make you a featured extra like our man MikeyG. Movie sets aren't that hard to find because they usually have little signs with part of the production's name and an arrow. This is to help the cast and crew find their way. When DrumLine was being filmed here, i almost followed the "DRUM-->" signs and asked if they needed extras (which they almost always do), but decided I made more money at work.
The sad part about being an extra is that it's long, tedious work, where they treat you like cattle and never let you forget it. I was an extra in Road Trip and our day started at 6 AM and went until 1 at night, and I did that for 5 days straight, and most of that time was spent sitting around playing cards and having to listen to people's plans on how they were going to become famous.
Still it's fun if you want to see how movies are made.
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Peeing sitting down is the gift you give yourself.