I've just gone through the annual ritual of sorting out my car and home insurance and there were some interesting observations and tricks that I saw the insurance companies playing.
First of all, when you receive the renewal notice, if you want to stay with the same insurance company, you can still save about $20 on your car insurance or $70 on your home insurance by getting a new quote from the same insurance company online. This worked for me with RAC.
With home and contents insurance, I noticed that the amount insured for both the home and contents had increased by 5%. Standard practice but if you think you don't need to index your house to the 5% inflation assumption, you can manually adjust your amount insured down to what you want which will save you on your premium.
Also, it pays to shop around. Take some time to go through at least two other insurance company websites to get different quotes before committing yourself to another year with your existing company. Don't be deceived - their loyalty reward is often much less than what you can get from a rival insurance company - I'm particularly looking at SGIO who quoted my car insurance at $1,017 compared to RAC which was $557.
When entering your details in getting a new quote, watch out for changes to your selected variables. For example, when I changed the date to start my insurance on the RAC website, my excess figures changed as well from $500 to $650.
Of course everyone's experiences will vary but the above should save you a few hundred dollars. To those who can't be bothered shopping around and happy to pay the lazy tax, sorry I wasted your time reading this :)