The bottom line is you never really know what you are buying, but a few points to consider.
If you live in the country try shopping at a local farm shop. On the whole, the produce is organic and they are often a lot cheaper than Waitrose etc.
Also, in season, take a drive through a country village and buy produce from peoples gardens. If unfamiliar with this there is usually an honesty box. I doubt if Mr Jones uses any industrial pesticides on his allotment.
Further, a recent report has stated there is no substantial evidence that organic food is any better for you. Remember Dr Gillian McKeith is NOT a real doctor.
I tend to eat well and although healthy am not fastidious about food. The only food I insist on buying organic is ready made salad (rocket, spinach etc) because I like it straight from the bag. As long as you wash your fruit, and steam your veggies, I personally couldn't give a monkeys.
On a related note, I refuse to buy "fair trade". A banana planter in the third world is paid the same whether picking economy or Fair Trade. The only people getting rich are the owners and the often corrupt governments.