The most common mistake I've seen is not agreeing on what arrows represent: control or data. Does A-(customer data)->B mean A asks B for data or A sends customer data to B?
Of course, sequence diagrams make it clear with two separate arrows when control and data flow in different directions, but a lot of diagrams are of the "plain old boxes and arrows" variety.
Of course, sequence diagrams make it clear with two separate arrows when control and data flow in different directions, but a lot of diagrams are of the "plain old boxes and arrows" variety.