Tiff, how do you become an immigration officer? They're looking for someone with a certain personality, and with a degree in a relevant field. I'm finishing up my Criminology degree so I essentially do all the work of a full-fledged officer without getting their pay or benefits (yet).
I mean, when did the idea pop into your head? My university has a co-op program where students can network with professional and governmental fields relevant to their studies, and Citizenship & Immigration Canada has a lot to do with Criminology, so that was my foot in the door. And I study a lot of governmental legislation in my law classes so that helps. Plus my dad's an immigrant-turned-citizen, so it's always been an interest for me.
Are you really stern, or friendly and smiley? Depends. When someone first walks up to the counter, I'm neutral but polite, because I'm Canadian and I have to be.

We, and customs officers, are trained to essentially make a decision on our "feel" for a person within 30 seconds of interacting with them and go with our instincts, so that decides whether I'm happy and smiley (which is about 55% of the time) or whether I'm a screaming bitch (about 20% of the time). Which brings me to...
And do you have a lot of trouble? Yes. Lots. And it surprised me how much crap goes on when I first started. Within my first four months I'd seen countless drug mules, aliens, sex trade workers and one guy suspected to have links to terrorism. In fact, last month I got roughed up by one particularly unruly drug mule coming off of a meth high (I still don't know how it happened).
There are a LOT of problems with the current immigration system in Canada. I've had to "land" new permanent residents and allow them to come into the country even though they've lied to me, are probably only in a "relationship of convenience" with their sponsor, or simply I just don't have enough concrete proof to deny them entry. I used to be very critical of how our country could have managed to let a few terrorists (allegedly) slip in and out to the States, but I wish people could see the high volume and the type of people that we DO apprehend on a daily basis (I would say we typically apprehend about a dozen illegals on an 8-hr shift) before they judge us on missing the odd few. There's a LOT of bad people out there.
I've got a lot of horror stories from the average day at work, and it still never fails to amaze me what people would do to get into the country.
"It's not always about you!!!" (But if you think I'm referring to you anyway, then I probably am.)
"Good luck returning my ass!" - Wilhemina Slater
"This is my breakfast, lunch and f***ing dinner right here. I'm not even f***in' joking." - Colin Farrell