Composting question

I live in a condo and have a terrace that 2 other condo owners have access to.  I have a few planters that I plan to plant herbs.  My question is, what is the easiest way to compost?  If this was you, what would you do with your waste like egg shells, fruit and veggie bits and pieces and also my cat waste?  I am considering getting  biodegradable bags of course, but I seem limited when it comes to the organic material....give it to someone with a garden???  I already have curbside recycling so that is good, plus I am already thinking twice about what kind of products I buy.  Still, I am stuck with the composting thing. Any ideas?  Thanks.  Have a great day.