The cheapest one is on www.aarpdriversafety.org/ The online course fee is only $15.95 for AARP members and $19.95 for non-members. There is no age requirement. It will qualify you for 10-15% for your current premium.
2. Raise your Liability coverage from minimum to 50,000/100,000 (if your state minimum is 25,000/50,000) or one level up from whatever the state minimum is.
This will RAISE your current insurance premium. If you are not thinking about switching, you should not do this. But if you switch insurance company AFTER raising the liability, you will receive a 10-15% discount from the new company.
3. Raise your deductible to at least $500.
Preferred companies like Metlife, Nationwide, etc usually give better rates to customers than non-preferred ones. However, they will also consider dropping a customer if he/she has more than 2 at-fault accidents/traffic violations within a 5-year period. So people usually will fix small problems when they cost less than $500. In those cases, a $250 deductible is meaningless because you will not make small claims anyways.
4. If your car is worth less than $3000, you can have only liability insurance.
In these cases, if you total your car, the most insurance companies will pay is $3,000. If you stop paying comprehensive insurance, you can save $3,000 in a few years.
5. Muli car discount, Car and home, etc. Everyone knows about them.