How do I present evidence in a small claims case?

If the matter goes to an actual trial, even in small claims court, you may need witnesses who will actually testify to what they actually observed. The small claims court may not accept an affidavit or someone's out of court or hearsay statement.

In some cases you may need original documents, and must be able to introduce them just as at a regular trial - and this sometimes can be very difficult. (Documents must be authenticated to show that they are what they purport to be.) Some small claims courts allow you to introduce copies of bills and other records, but only if you have sent the other side copies sufficiently far in advance.

You may need experts who would testify to things that ordinary laymen are not available. For example, the damage to your car may have to be proven - and as a layperson does not know what it costs to fix cars - it may take an expert in car repairs to prove the damages done. If you haven't been able to afford to have the repairs made you'll need some expert to say what it will cost. Your statement, "they said it would cost $X," is hearsay; the other side can't cross examine the person who told that to you unless the person was in court. If you had the repair made you'll have a repair bill. While that may show what you paid - it is not necessarily what you should have paid.