Welcome! Since you've been reading around it's likely you've discovered The Daily Plate and Fitday for tracking calories.
If you're overwhelmed (understandable) I'd start simple. I'd begin by not changing a thing with food and merely track what you do eat right now. Every bite, be totally honest. A week or so, at least a few days to see patterns in your eating.
Once you've got a few days of 'normal' eating tracked you'll be better able to analyze your diet, see where you can begin cutting out unhealthy foods, add more healthy in. You could post a true day's intake here, get some ideas on how to better your diet.
I'd set a start date and not go by anything vague. Once you begin, you begin - I find for me concrete goals like that work so well. That's about all I did as far as planning ahead, told myself I'd start on New Year's Day and hyped myself up for about a week. In retrospect I would have better served myself by actually coming up with a game plan, figuring out what my previous intake was.
ETA: I don't know your living situation, but while you're tracking your eating you can also begin to rid yourself of unnecessary junk, clean the cabinets and fridge - sort of organize everything for your start date - go shopping for eating clean, make grocery lists, look at different gyms (if you're going to work out at a gym) - plan ahead. That way you'll start with all the planning work done. I think for many, it's hard to begin new habits without an action plan, it's easy to become overwhelmed and quit in the beginning otherwise.
As far as finding you've consumed too much at the end of the day - totally preventable and an easy solution is to track while it's happening. Tracking as I eat - or before I've eaten, not at the end of the day is critical for me. I wouldn't be honest with myself, and I hate math
Even when going out to eat, with The Daily Plate I can look up nutritional information beforehand and have no excuse for my intake.