[In process. This article is incomplete and a work-in-progress. A complete draft will probably not be done for at least several days. Jan. 12, 2012 Espiegel123]
Making free-floating soap bubbles -- especially giant ones -- can be tricky. Everyone, even the most experienced bubbleheads, have days when they can't get a bubble to close or can't get a closed bubble to last more than a few seconds. For a beginner, it is very hard to know if the problem is the "bubble juice", the equipment, or the environment. This article is not comprehensive but should give you a good start on diagnosing your problems.
If you are just getting started, keep it simple: the bubble juice and your equipment. A simple recipe that has just water, detergent, a single polymer (probably PEO or HEC) and (optionally) either baking soda and citric acid or baking powder will perform just as well as more complex recipes. Many people (the author included) spend a lot of time working on complicated recipes when equipment or the environment is a much bigger factor.
For giant bubbles, start with a simple reliable recipe such as Edward's Basic Recipe or Mike's Gooey Mix or the HEC-Based bubble recip, or purchase a reliable commercial product such as Bubble Thing Powder, Cricket Hill Powder, or Bangwool or Beeboo. If you are having trouble making bubbles with these reliable recipes (using the ingredients specified in the recipes), the problem may be some combination of equipment or environment or (but probably not) water.
One helpful thing to do -- even if you are intending to create giant bubbles -- is to use a small plastic one (such as come in bottles of dime-store bubble solution) to see how many bubbles per dip you can get with gentle blowing and to watch them. Most good giant bubble solutions will produce a stream of 10 or more (at least 5) bubbles per dip. Many will create many more than that. If you are having trouble blowing this many bubbles with one dip of a recipe that is known to be good for making giant bubbles, the bubble juice itself may be the issue--either improper mixing or an ingredients problem. (More on that later). If you have no problem blowing this many bubbles then the problems you are experiencing are probably due to environmental factors (more on that later) or equipment issues (more on that later).
Water is rarely the issue, but in exceptional cases, the problem may be the water. If you are using a reliable recipe with which others have had success with (i.e. one of the recipes mentioned above or most others in the Recipes section) 'and' you are using a reliable detergent, try making up a small batch using distilled water to see if that improves things. If it does improve things then your water source is probably a problem.
Some pros always use distilled water because the result is very consistent which is a requirement if you are relying on predictable behavior. In most cases tap water is preferable since the trace minerals are usually beneficial to the bubbles, but there are cases where a locale's tap water has too much of the wrong minerals to work. Also, the water supply may vary. For example, the water's mineral content may vary seasonally or might change temporarily if work (such as pipe replacement) is being done on the water system.