I get my extra serotonin by taking St John's Wort from about October to May, I use a light box during the same months (well, I stop about March) and I run. They all produce serotonin.
All of these keep me 'up', to the extent that, since a major 6 month depression 8 years ago (before I knew about these things), I don't have to take anything else. Mine is SAD - winter related, but its still a lack of serotonin.

The things above take a while to get going. Exercise is pretty immediate, the light box takes a week or so and the St John's wort a month or so.

I'd say give it a go. I have no side effects from the St John's Wort, though you have to watch it in conjunction with some other medicines, especially the BC pill, which it can stop working (oops!). The other two are side effect free (well, the exercise has other good side effects).

I've also just read an article that says that 5-HTP (5 hydroxytryptophan) that you can buy from the health food shop, is very effective at producing serotonin and therefore reducing depression too - I might try that as well. Recommended dose, 100mg (up to 300mg).

Hope this helps, good luck, Jay