On the GMAT, you are required to specify the schools to which you want to send your scores before you even see the first question.
What I did was to make a fair assessment of my score range. Then I identifeied which schools had a decent acceptance rate for each score range.
This way, you can be reasonably sure of your guess for the score.
Further, let this be the last thought on your mind at the GMAT. It costs only $13 for additional score reporting.
Whether your scores are actually reported depends on whether you accept or reject your GMAT.