Really this didn't happen overnight. We had an idea to get better grip of our finances but the 'how?' took some adjusting. Ok a LOT of adjusting! :)
The first step we took was just talking. Finances for a couple don't work if only one person is on board. Sure you can help some by adjusting your views of money, but the biggest impact is if both of you are on board.
Our first step was just saving every. single. receipt for a whole month. When we got home from shopping we would go back over them and highlight all the non- necessary things we bought and the impulse buys. Then we stuck them in a baggie. At the end of the month we were shocked when we looked over them. Over 50% of each receipt had impulse buys on them or stuff we didn't need! Things from what we 'wanted' or groceries we already had on hand, but couldn't find due to a poor organized pantry. We were shocked.
We moved on from that step. We researched the envelope system which uses only cash and decided it was for us. Then we started meal planning, because the biggest bulk of our receipts was food. Food is usually the one area that you can make the most adjustments to help out your budget. We meal planned our menu each week. We wrote out a grocery list and stuck to it. It was amazing to see how much we saved just with these few steps. It all helped to inspire us to keep going on it and the keep our goals for living debt free in sight!