At this point your guess is as good as anyone else - but mostly this is what I do to boost my success rate (currently doing Goldsmithing, rank 5, things may differ from class to class I don't know).
Basically I know:
- Rapid synthesis focuses on higher progress with small quality gain.
- Standard synthesis focuses on a goof mix of both quality and progress.
- & Bold synthesis is the other end of the spectrum with focus on higher quality with little progress.
I watch the color of the orb when I'm synthesizing: I have noticed the following;
- Gold orb increases your chance of a successful synthesis by the largest amount.
- White orb gives you a decent chance at a successful synthesis.
- Red orb gives you the worse chance at a successful synthesis.
- Random colors gives you a random chance.
So when I get gold orb and I wanna boost my progress I go with Rapid synthesis; on the other hand if I have a gold orb and my progress is fairly high, but I want to boost my quality, I do bold synthesis. For white orb I almost always go with rapid synthesis because the chance of failing is still higher than gold orb, and if i fail a bold synthesis I take a big hit on durability. For random colors I usually stick to standard synthesis.
When I get the red orb I use the "wait" option to change the color of the orb, crossing my fingers I get a better color and a better chance at a successful synthesis. Of course, you almost always change from red to atleast random colors which automatically duplicates your chances on a success.
Lastly there is the element destabilizing - so far i'm still playing around with this but its obvious if the element is unstable and you "break" it you take a huge hit on durability so what I usually do is use the "wait" option a couple times and/or let the timer run out, sometimes the element will stabilize and I can carry on with my craft a little more confidently.
Also, make sure you're not doing crafts that are too high above your rank - for example, when you get a leve that says requires "Craft Class" rank 5, it means you're not going to be too successful before rank 5 (different than XI where we basically knew when a certain craft capped at, if you've ever played XI)...anyway, I hope this is of some help, just keep messing around with it, its fun when things start falling into place.
Finally, check out this website for craft recipes and a million other things, you can pick out low rank recipes and work at them: http://ffxiv.yg.com/
Best of luck.