Zam has a very nice in-depth guide to crafting but personally I feel that there a bit more information needed to the craft beginner in regards to how to react to the various "orbs" colours and such.
Steady Colours:
White - What is supposed to be the most stable ocasion but can still fail sometimes, even in your first attempt. Altough this colour can handle any crafting choice it gives your more benefit when you use Standard Synthesis. This will usually give a progression of between 10-20%, quality increase of 3-12 and can lose up to 10 durability even if successful. Be aware that a fail can cause 0-1% progresion, 0 quality and 15-20 loss in durability.
Yellow - Maybe not as stable as the white there is still a good chance your synthesis will be successful. Although you can "safely" use Standard Synthesis on this colour, it tends to give a benefit to Rapid Synthesis enabling an advance of up to 40% (that I have seen) with little to no quality. Since the "fix" in early October Rapid Synthesis is no longer a sure thing as it appears to have received a higher Fail rate with gib losses of durability (~20).
Red - Once again it might not be as stable as white but read seems to have an above average change of successful synthesis. Although you can "safely" use Standard Synthesis on this colour, it tends to give a benefit to Bold Synthesis with sometimesa considerable increase in quality along with some or none in progress. I have seen quality increases of ~50 on one Bold sysnthesis alone with 0-10% progress and no loss in durability. Of course if failed it can cause huge loss of durability (I have experiences loosing 35 durability in one go and on another ocasion 55 lost durability in two failed Bold Sysnthesis in a row).
Flashing Lights.
This is when you can notice a change in size or colour in the orb and represents your crystal becoming unstable. In the begining I used to just Wait every time this happens but this can sometimes cause you to wait up to 5 or 6 times causing a total durability loss of over 10 which can be the difference between success or failure. If I'm attempting a recepy which I know that is below my rank and/or easy I now tend to only wait once and even if the result is still blinking to go ahead with Standard Synthesis. There is a a very high probability that the Standar Synthesis is successful and this way you only lost 1 durability to get the crystal a bit more stable.
Destabilized Crystal.
This is when you can see not only a flashing light but also a coloured ring around the orb (you also get a text message on your synthesis log). This is another case that in the begining I just used Wait over and over again to try and get the orb stable but the great majority of the cases with no success. Just as with flashing lights if the recepy is of a lower rank than yourself I find it that Wait - Standard Synthesis works quite well although most times you need to do it twice before the orb gets stable. There was some mention from SE (cant remember where) that in this condition you might be able to get great returns from the Synthesis, kind of great risk - great reward, but I haven't really tried it myself.
From my experience which is only armourer 43 these simple "rules" will work for the great majority of the time but there are situations that just fall outside these ideas. If you have failed on a Steady Colour twice in a row you might want to consider to use Wait even if you have another steady colour. It might happen that you have the orb on at 95% progress and just need to risk it because of low durability and it will sometimes work.
Basically this is my point of view which I decided to let other crafters know so that it might be of some help, do not make me responsable for any failed synthesis you might have had following these rules or advices.