When selecting an internal account on a check, one question needs to be asked. What money is going to be used to pay this expense? Are Church - General Operation funds (tithe money) to be used or should some other designated funds be used? In some cases NYI funds, Faith Promise or the Building Fund may be used depending on what the check is for.
What is being paid for will determine what internal account should be selected. Building Fund money wouldn't be used to pay for Sunday School supplies. However, General Operating or tithe would be used to pay for the electric and water bills. Typically, WEF or Faith Promise funds are used to pay for World Evangelism Fund, but Faith Promise would not be used to pay for the District allocation (Faith Promise is generally reserved for World Evangelism Fund). The district allocation would typically be paid out of General Operating.
The internal accounts should represent the different offerings that are taken up on a regular basis so that when a deposit is made the funds can be deposited into an account for that offering. Then when writing a check, the appropriate offering money can be used for the check by selecting the internal account for that offering. This process provides a way to track designated funds and ensure the funds get used for the purpose for which they have been given.