Further to #1:
1) Use consistent prefixes and suffixes throughout your schema. For your internal key fields, end them ALL with ID, or Num, or Key or whatever. Just don't end one internal key field name with ID, another with Key, and another with Num. Similarly, don't start one phone number field with phn, another with tel and another with phone.
2) Whenever possible, if two tables are related by a common key field, name the fields exactly the same in the two tables. It drives me crazy when some DBA figures I can intuitively deduce that EmpID in one field is the key to the field UserNum in another table.