Have your wedding on a day other than a Saturday. Saturday is peak wedding day so having it on a Sunday or during the week can be cheaper. Also, use family and friends skills to your advantage. If you have a family member or friend who can take exceptionally good photos get them to do the photos, if someone is good at cake making take advantage of that etc. They will feel special because they are involved in your special day and you can save thousands!
Have a ****tail reception rather than a sit down, depending on how formal you want things. This is a good casual thing and great way to allow people to mingle. It's also heaps cheaper.
Make your own invitations, wedding programs etc or have a crafty family member or friend do it for you.
Most importantly, know what you want and set a budget. Try to haggle with the price of somethings if you can. Unfortunately weddings are big business and as soon as you put the word wedding in the sentence the price seems to skyrocket!