1. Either follow a general 'one size suits all' approach (not that I believe in them, though it is a good way to get in to good habits and reduce the out and out crap in your diet). So, next time you are in the super market, buy products without added sugars, like pure fruit juice (NOT with aspartame). A brief look at food groups might look like this :
Red meat : occasional, organic if affordable. (Yes, really re : organic - I used to work in the health industry, and all independent sources that I spoke to, papers I read, authors all recommended that if you are going to buy organic, then meat should be the first choice, unless someone is vegetarian of course (vegetable or 'live foods' if vegan). In which case then I would suggest dairy). Better to eat less but higher quality foods, doesn't mean you have to starve. No prizes for trying to do it quickly, you are more likely fail.
Poultry : turkey / chicken.
Fish : oily ones such as mackerel, salmon, herring.
Eggs : excellent source of protein, better to boil than any other method, saves destroying any EFA's.
Dairy : again, like red meat, less often but in balance adds variety.
Vegetable proteins : nuts / seeds / e.g. almond butter, higher protein veg like green beans / peas. Tofu, water melon seeds.
Fats and Oils : Ghee, organic butter (so cheap), flax seed oil (don't heat any efa rich oil!) Olive oil, coconut oil, pumpkin seeds oil etc.
Carbs : low glycemic, 'nuff said.
Fruits : nature's best snack.
Live foods (veg) : experiment with something, even if it's roasted parsnips! Failing that, buy a green food supplement. Spirulina is good, as is Chlorella.
Beverages : herb teas, diluted juices, a little weak tea is ok, very little coffee.
Spices : cinammon, rosemary, oregano etc. Spices were used for medicial purposes throughout history.
If and when you want to look at belief systems, try authors like Patrick Holford, Peter D'adamo : blood type / genotype diet (based more on individuality than any other known - which I feel is thee and only way to go forward, ultimately, e.g. genetics.)
Good luck, above all enjoy it and do it gradually at your own pace.