Ok, I’ll start off with produce since most people eat fruits, veggies in their daily diet.
Obviously the best way for yourself and the environment is to NOT buy fruits, veggies in cans or plastic containers.
You want to buy fresh and preferably local to you. I know this can be difficult for those who may want something that isn’t locally grown or is out of season but there are ways around that. You can can items when in season to enjoy later to help alleviate that problem.

Here are a few ways to make green changes!

Light Green (where you’re making some changes)
1)Eat organic when possible
2)Wash and peel produce (especially if it’s not organic)
3)Eat a variety of produce to get all the nutrients you need

Green (where you’re making even more changes)
1)Buy from local markets — if you don’t know where a local farm market is you can visit http://www.localharvest.org to find those in your area

Dark Green (where you’re making big changes to help)
1)Grow your own produce, fruit trees
2)Buy from local markets even if not organic because you can wash, peel and it’ll have less of an effect on the environment than the gas, waste, carbon used to transport from other further away areas.
3)Join a food co-op. They also can be found on http://www.localharvest.org and now in some local papers and on http://www.backpage.com and http://www.craigslist.org there are some advertised, depending on your area.

You can also find more information on these sites:
http://www.organicconsumers.org
http://www.slowfoodusa.org
http://www.sustainabletable.org
http://www.centerforfoodsafety.org
http://www.ucsaction.org
http://www.localharvest.org