In most cases of fischer esterification, the carboxylic acid is the more "valuable" piece and the alcohol is used in excess. let's say you are making the ethyl ester of an acid and use the ethanol in excess. what technique would be used to remove the excess ethanol?

There are a lot of separation processes. To name a few, these can be distillation, centrifugation, extraction, membrane or sorption process and many other. To know which is the best technique, you should know the property between two substances that have a stark difference. In this case, it is the polarity. Ethyl alcohol is more polar than ethyl ester and less dense. Thus, these two won't mix. So, take advantage of their density difference by decantation or centrifugation.

Temperature and pressure