There are several things to watch for when selecting mature coconuts:

• There should be liquid, or "water," inside the coconut. A gentle shake will disclose this.
  
  
• There should be no mold or mildew on the outside, especially around the "eyes." This may be a sign of mold inside the coconut. Tiny black spots may be early mildew or mold.
  
  
• There should be no cracks in the shell. The shell should be intact, protecting the meat inside.

Using a knife, clean the area around that eye, then begin digging out the covering. If your knife is small enough (and the eye is big enough) you can dig right through the meat and into the inside of the coconut.

Most likely you will need to use a drill bit or screwdriver. I use a drill bit and twist it by hand through the meat. I prefer this as it removes the meat instead of pushing some into the shell. Any pieces floating around inside the shell may clog when draining the coconut.

I keep a few sizes of "kitchen" drill bits for various sized coconut eyes. I always use the largest one that will fit.

When you break through the meat to the inside of the coconut, there may be a hissing sound. The coconut is just "depressurizing". There may be a slight vacuum effect inside the shell. This is normal. If there is pressure pushing out, this may mean bacterial growth is inside. If the meat is very soft and there is no difference in pressure, the coconut is likely bad, but check the water and meat to be sure.

Other Vegetarian/Vegan Links:
Vegetarian Protein Sources / Vegetarian Calcium Sources / Vegetarian Iron Sources / Vegetarian Fiber Sources / Vegetarian Fat Sources / Vegetarian Magnesium Sources \ Vegan Recipes /
Vegetarian Organizations \ Famous Vegetarians \
Vegetarian Events \ Extensive Vegetarian & Vegan Links / Vegan Travel