I've checked the four first pages and saw nothing, so there it goes...
This tip is a bit straightforward, but many people underestimate it. The real deal is that it requires very low effort and yields very good profits.
As you know, most of the daily jewelcrafting quests require to craft certain green quality gems and turning them to the vendor. Use that on your advantage.They sell for 30-50g/each like candy. I've been doing this for a week now in my high pop server, selling 60+ uncut gems each day.
If you are a jewelcrafter:
Keep EVERY green uncut gem you have and post them the day they're used for the daily quest. Get profits.
If you're not a jewelcrafter:
Keep track of cheap stacks of uncut gems. Many lazy jewelcrafters just dump them to the AH in big stacks after prospecting for blues, as low as ~12-15g/each. Keep them until they're required for the daily quest. If you are not a jewelcrafter, you may ask someone which one it is... or check the AH for the green uncut gems, the one used for the daily quest will be SIGNIFICANTLY more expensive than the others.