I first started to really think about the food I eat and how it is produced after I read The Omnivore’s Dilemma by Michael Pollan. Now I try to eat according to the simple principles that he outlined in Food Rules:
Eat food, mostly plants, not too much.
In this context, food refers roughly to things that your great grandmother would recognize as food, as opposed to all the artificial sounding ingredients that are ubiquitous now.
This article is a nice summary to healthy eating that seems to largely agree with what I have read elsewhere.
For eggs, I check this rating site to choose which brands to buy.