Benchmark hunters are in two camps regarding data carrying in the field - paper and paperless (digital equipment). In either case, the ["datasheet"]s, in some format, including the to-reach descriptive text, are a must. Be sure to bring any ["box score"] information for any mark that has a box-score.
If carrying paper datasheets, it is best to have them sorted by PID so that you can find them in your package easier. Before you staple them together for you trip, it is also good to include an overview map showing all the marks you will be looking for on your trip.
For data collection in paper mode, it is best to use a formatted paper you make yourself. Example fields to record are:
the order number of the mark - the first mark you searched for that day would be number 1, etc.
the compass direction of the 'distant' photo
the GPSr - generated waypoint number, if you're measuring the coordinates of a position-scaled mark
whether or not you found the PID
the condition of the PID
On a separate piece of paper, you could use a free format with just two fields - PID, comments. This is where you would record any new to-reach information, changes in existing to-reach information, and any other comments.