A good bug report is clear and concise. For ARQ, reduce the problem to a short dataset (20 triples should be enough; Turtle, N3 or N-triples preferred) and a query that illustrates the problem. State what you expected to happen as well as what did happen.
It also a good idea to check the documentation.
The SPARQL parser outputs a line and column number - it is usually correct in identifying the first point of a syntax error.
If you are reporting a failure that produces a stack trace, please
include the message, exception and the stack trace. Only if it is very
long, should you truncate the trace but please include the whole trace to
the point where it indicates it is entering ARQ (a package name starting
com.hp.hpl.java.query
) and one level which is your code.
If you are getting unexpected results, show the results you expect as well as what you actually get.
There is a testing format used by the Data Access Working Group and that is used for the scripted tests in the distribution.
The report should also include details of the execution environment:
java -cp ... arq.qparse 'your query'