Recycle as much as possible!
You can recycle clothes - not just via the clothing bank or charity shops, but at swapping parties or by restyling if your sewing skills are up to that.
You can recycle just about everything by putting it on eBay and wait for somebody to bid for something you no longer want or need.
Don't forget local community jumble sales and bazaars - an excellent way to offload unwanted gifts you may have been given and help a good cause at the same time!
You can also try recycling most items via a website called Freecycle - see below.
A good way to advertise and dispose of any goods you no longer want - the service is free. Somebody will almost certainly want what you what to get rid of, and it saves just throwing away perfectly good and useable things or taking them to landfill.