Bring The Ticket
This is a simple, "no brainer" that sometimes people forget or might not think of. The ticket may prove significant to show evidence of the charges being recorded improperly, or to show other discrepancies.
Bring A Printout of The Law That Applies
By looking at the law on paper in its word-for-word plain format you may be able to see ways in which the law was misapplied. Having this printout of the exact code will help you bolster any argument you may make as you will not have to rely on memory or the solicitor's reading of the law.
Bring Photos of the Area, or Diagrams of the Streets/Intersection
To help explain yourself it always helps to have visual aids. If one were questioning the accuracy of an officer's observation from a distance for instance, then one might either photograph the applicable areas or clearly diagram them to illustrate their point. This could be useful where a road sign was not visible due to limbs, the view around a corner is blocked, or some other aspect of the surroundings should be taken into account.
Bring yourself well dressed and well mannered
Visual Impressions matter in court. Presenting to the judge, solicitor, and courtroom personnel a clean image and polite manners shows you put time and thought into your appearance at court. This makes you more likely to make a good impression. By simply being well dressed and polite you may have your challenge more thoughtfully considered or the prosecution or judge may see more room for leniency in your case.
Bring any witnesses
If you had someone riding with you, or if there were any other witnesses to the incident that you know of and can bring with you then do so. This is only If you have a legitimate challenge to the citation and the witness will testify to your version of the event.