I've heard about people saying something like "eat 80% good food" (for a given time period) and like that idea. I think of it in terms of meals, days, and weeks. Allows you to have "cheat" days/meals as long as your intake is generally healthy. A general guideline that keeps you thinking about if what you're consuming is "good" or "bad" (granted it's never going to be absolute)
I know in the past I've definitely overeaten, so sometimes I try to go by the "eat until you're 80% full" guideline and not eat the "typical" 120% of what I should have for the given meal. (Not vouching for this source or anything, but wasn't aware of the actual term for this so leaving a link:
What is Your Hara Hachi Bu Point? – Cleveland Clinic)
These are food related things, but of course any type of routine, "safe" activity you can do to be active is also good.
Main things for me:
Pretty much no fast food
I don't eat out a ton in general (generally don't have full control of what's in your food)
Try to buy things with low salt/sugar (and other "bad" things)
Don't add sugar to things (food or drinks, including coffee)
Don't add salt to things (in general - of course seasonings/sauces will have some sodium)
Try to buy fresh versions of things
Make yourself eat some healthy snacks (which for me means having more of those around than unhealthy snacks)
Find healthy-ish things (alternatives) for desserts and try to eat less of it (or eat it less often)
Get yourself to like healthy versions of things (example for me: I don't really eat cereal except at night, but I get basic cereals with no sugar added. I eat it with whole milk that already has sugar)
Try not to eat just because you're bored/stressed/etc. - find a more productive outlet