The bottle you had last night was perfectly carbonated, the one you just opened was totally flat, and the one you’re about to open will gush all over the floor. When this happens, it’s time to take a closer look at your priming method.
The most common way to carbonate homebrew in bottles is to “prime” each bottle with a small dose of sugar. Yeast consumes this sugar and releases carbon dioxide, which, since the bottle is sealed, dissolves into the beer. The most popular way to introduce that sugar into a batch of homebrewed beer is to mix up a solution of dextrose (also called corn sugar) and water and add it to the bottling bucket as you rack the beer from secondary. If this is the method you follow, then there are a few steps of the process to examine.
Headspace
This is the least likely culprit but an easy one to fix if it happens to afflict you. The more headspace there is in a bottle, relative to the total volume, the more carbonated that bottle will become. That’s why it’s important to push the bottling wand all the way down and allow beer to come all the way up to the lip of the bottle. When you remove the wand, the perfect amount of headspace will remain for proper carbonation.