Too sweet. Of course, this assumes that you were not going for a sweet beer anyway, in which case no problem. Let us not forget that even a solid or "fresh beer" can be too sweet, but definitely do not want a bitter. There are two main reasons for this, it is an excess of malt, where the action is to add half a teaspoon of his boot from the fermentation of the bottle to the boat.
The other is the lack of attenuation, which is where the density is lower than 1010. Unfortunately there is no cure for this, and if the mixture is completely undrinkable (we all know someone who will) all you can do is to discard it.
Too lively. Problem is quite common and relatively easy to fix. There are three main reasons here. Excessive use of priming sugar when you need to decant INRO a large deck of the vessel, avoiding contamination. Too high a storage temperature. Simply remove the correct temperature between 50-55F. Too high a weight and when bottled. Add half teaspoon boot of the bottle, not too tightly sealed, and release the gas a day. Yeast
Too much bite. As its name indicates it is an excess of yeast, an intense acrid bitterness. An excess of yeast can be removed from the periphery of the fermentation vessel with waste, simply using a damp cloth. A yeast suspension can still be treated by the addition of more finings. Sometimes, storage at too high a temperature to cause sediment to rise and disperse. Simply remove the correct temperature of 50-55F.
The lack of a good head. Four main causes of this condition. Using malt defective. Nothing to do here, except to throw and start again. Very short period of maturation. Ah, the impatience of youth! Can be recovered by pouring into a large covered, avoiding the use of the bottle the boot, and switch to a slightly higher temperature.
Lack of dextrins, which means that the mass has reached a temperature of less than 152F. You can try the temperature of heating. The reason is simple using a drinking vessel that has not been properly washed and rinsed. Clean glasses are a necessity.
Beer tastes "off." This may be caused by the decomposition of dead yeast cells. Quite by racking.
Cloudy beer. In this controversial, as some drinkers do not mind as long as the taste and flavor are good. However, the majority of beer drinkers like to see a good product of course. Causes storage at too high a temperature. Just go somewhere cool. Insufficient sievings grain malt and hops. Finings adding that usually resolve. Excessive use of finings. Nothing to do, either as a drink or discard. Very few finings. Add more carefully. Filtering ineffective or too soon. New filter.
Well, there you have it. If you are thinking that you just have to go so bad that just is not worth it. Do not be discouraged. They tend to produce a perfectly drinkable beer. It's just useful to know some things that could go wrong and how to fix them if possible.
Of course, the probability that things go wrong is drastically reduced if you find a good recipe for beer, and stick to it. When you have become a brewer reasonably competent, then you can go and experiment.