How to identify the brewed beer good or bad?

How to identify the brewed beer good or bad?
1.First of all, whether the beer is within the shelf life. The taste of beer over the shelf life will be affected;
2. Carbon diocide is sufficient, when the opening of carbon dioxide bubbles rise;
3.Beer bubble rise when putting in cup, white and delicate, high-quality beer foam persistence should  be more than 3 minutes;
4. Beer clear and transparent, full of luster, no obvious suspended solids or other inpurities;
5.After drinking should be refreshing felling soft, and have Kou nouth and happy bitter taste, no other amell;
6.Light beer should have hops fragrance, dark beer should have malt flavor. You can master this knowledge can determine the quality of a bottle of beer.