Start with just cooking and eating whole foods, I wouldn't try to go full keto out the gate. It's tough to keep to, since even vegetables can throw you out of ketosis. Onions and peppers were my downfall. Avoid adding sugar to anything, or anything that has added sugar, and you're more or less good to go IMO. My go to is red meat, usually some kind of steak like a top round, broccolli, and a sweet potato. Sometimes I go with rice instead of the potato. Chili is also a good option, though usually higher in sugar from the tomatoes and onion.