Even the best bakers make a mistake every now and then when preparing a dish. For cake bakers, the slightest misread of an ingredient can throw a whole recipe off. One of the issues that may come up is the consistency of the cake batter. Thin cake batter is a result of excess liquid, and could result in shrunken cake that has a tough texture. If you notice that your batter is somewhat thin, a little extra beating and flour should help thicken it up.
Beat the batter on low to medium speed. Use the amount of time stated in the recipe, even if you have already done this step. Beating will help put air into the batter, which thickens it up.
Add flour to the mixture one tablespoon at a time.
Beat the batter between each addition of flour until you reach your desired consistency.