Sounds like you might want to start with some non-food goals and habits first. Like:
- 8-8oz glasses of water each day
- 2+ fruits/veggies each day
- 10+ minutes of fitness each day
- 7-8 hours of sleep each night
Then, move on to tracking what you eat. Whatever it is - just track it. Then, just look for ways to cut out 50 or 100 calories each day. That could be as easy as giving up a soda a day!
Once you have made things like this a habit it will be much easier to work on portion control around others.