Almost two years ago, I purchased three citrus trees (Dwarf Venous Orange, Dwarf Key Lime, Dwarf Meyer Lemon). The lemon tree had flowers on it, which indeed produced two lovely fruits. Since then, the trees not been able to produce any other fruit or flowers. Recently, I've learned a few things that I hope will help my citrus trees thrive.
1. Don't over react to all the caution about watering lightly. In my case, I suspect I was under-watering for too long. Terracotta pots are best because they breathe, which reduces the possibility of over-watering. Water generously and then empty the drip trays after the excess drains.
2. Use a special citrus fertilizer. Citrus trees tend to suffer chlorosis. The fertilizer I use is Jack's Classic Citrus FeED.
3. Although my plants are near a window, I can hardly count on Mother Nature to provide enough light. Plant grow bulbs are plentiful---incandescent, compact florescent, LED, red and blue spectrum, and much more. Supplemental lighting is essential. My trees get about 12-16 hours of light per day.
4. My house is cool, usually around 60 degrees or even a little less where the citrus trees are located. I suspect that my trees would like it a pinch warmer. I've recently placed them on seedling heat mats to keep their roots warm.
5. Don't bother growing trees from seeds saved from a piece of fruit at the grocery store. They're easy to germinate and grow, but you have a 50/50 chance of growing something wildly sour and icky.
6. Humidity is important to citrus. If you don't have a humidifier on your furnace, mist the trees frequently or build a humidity tray.
Good luck! If you have tips to share, please comment--I'd love to hear from you!