To begin with, remember that the definition of a "Lemon" varies from state to state according to each state's Lemon Law. For instance motorcycles are covered in some states and expressly excluded in others. This is why if you feel you have a possible lemon law or breach of warranty case, you should immediately contact an attorney who handles this type of case in your state who will do a "free case evaluation" to determine exactly what your rights are under your particular state's laws. Remember, any delay can harm your case. You can find a listing of preferred attorneys that handle Lemon Law cases at the beginning of each State Lemon Law listings.
Do NOT consider any firm that wants to charge you for the initial consultation to determine if you have a case. If you do have a legitimate Lemon Law case, you may be entitled to a refund or replacement vehicle that includes your attorney's fees and costs, so any experienced Lemon Law attorney will not charge "up front" fees for taking your case.
For your case evaluation, you will need the documentation of your vehicle's defect(s) and your efforts to get the defect(s) repaired. A "defect" can be any problem with the engine, transmission, brakes, steering, water/oil leaks, paint defects, bad smells, vibrations, rattles, electrical, or almost any other problem that you've tried to have repaired multiple times (usually (4) or more attempts, although some states have reduced this to (2) repair attempts where the defect poses a serious safety threat) OR where the defect(s) have caused your vehicle to be out of service due to repair, usually for a total of 30 or more days during the first year of ownership. Once again, because the application of these rules vary from state to state, you need to contact an attorney for advice in these matters..
So gather up your "repair invoices" and always make sure your repair invoice accurately reflects the date you dropped off the vehicle for repair, the date you picked up the vehicle when the repairs were completed, as well as your complaints in your own words, not the dealership's. A service rep or manager at a dealership may try to write your complaint up as a "new and different problem" rather than a "recurring one" that would be covered by the Lemon Law of your state. Always save your repair invoices.
Also, try to have the paperwork/contract from the your original vehicle purchase transaction including your payment book, if you financed your purchase.
Additionally there are consumer advocate groups, departments of your state attorney general's office and "Legal Aid" sources that may be available in your area - check your telephone book.