We have three big olive trees in our backyard, but we usually leave the fruit to the birds (Wax-Eyes especially seem to love gorging themselves on olives). But earlier this year I saw some instructions for preserving your own olives in the NZ Gardener magazine and decided to give it a go.
The steps themselves are pretty simple, but the process is time-consuming. Before you even bottle the olives you have to remove some of their bitterness. The easiest way to do this is to soak them in water for a reasonable length of time, changing the water often. Of course if you like crisp, bitter olives, you can bottle them in brine pretty much straight away.
I picked olives off two of our trees (large black fruit on one tree and smaller green/brown fruit on another tree) and soaked them for about 40 days in clean buckets in our laundry sink. I changed the water often, but it certainly wasn't every day. At the weekend I finally got around to reclaiming the sink and bottling the olives in brine. They now have to pickle for another three months before we can eat them. I'll update you once we try them.
I've had a couple of friends ask me why I would go to so much trouble when I could just pop to the shops and buy a jar of olives for $5. I'm hoping the proof is in the tasting...