There can be many causes for a light ticking under the hood. Unless you get out a stethoscope it's not something worth guessing about. However, just for jollies I'll list what I have encountered.
1) Bad valve lifter. Had one in a 1978 Riviera that made it sound like a diesel on a cold morning, once the engine warmed up it was fine.
2) Bad bearing in a water pump. Sounded exactly like a poorly adjusted valve lash. Found it by using an extra long screwdriver as a makeshift stethoscope.
3) Mixing motor oils. With some of the cheap oils sold in convenience stores this can produce a wax like precipitate. After adding 2 quarts to a 1979 Monza the iron duke 4 started with the worst valve noise I have evr heard about 500 feet from the convenience store. Fortunatelly there was an old fashioned service station on the next block and I got a quick oil change before any damage was done. Now I always travel with some spare oil in my car.
4) Bad PCV valve. Put a new one in for about 3 bucks and the noise was no more.
5) Bad check valve on the EGR system. Left in alone until it froze up solid. Still driving that car and it's almost to 170K miles and runs smooth.
6) Poorly set valve lash. Yeah, I have fooled around with mechanical valve lifters and sometimes haven't set them perfectly on the first attempt. If you've ever been on your back setting the lash on an old air cooled Beetle, you'll understand why. That's where I learned to check everything 3 times before buttoning it up and starting the engine.
A lot of this won't apply to an engine as modern as yours. Got to Sears and get the longest philips head screwdriver they have. They make an excellent cheap stethoscope. Put the tip on an area you want to listen to and jam the handle against your ear. When you get close to the source, you will hear the noise get louder. Just be damn careful around the belt, if it catches the screwdriver it will launch it like a missle. BTW, I have not had that experience because I have always been very very careful when doing this.
Anyhow, that's how I would approach this problem. I like to know the cause before going to a mechanic. Fact is, I have never had very good luck with letting someone else do work on my cars.
