Hi Spangly, not sure if any of my tips will help but here goes. I've been maintaining for over a year now so I've finally accepted that I AM a maintainer and not just still in the trial stage....and god that feels good!
1. I weigh myself every day, as has been said, a lot of damage can be done in a week and trying to sort it before it's a huge problem is the best way for me to tackle it.
2. I have a happy box weight wise and won't let myself go above it. It actually has quite a bit of leeway as there is 7lb difference between the lowest and the highest. 7lb sounds a lot but for me it's giving myself permission to have a decent Christmas/Holiday etc without being too fanatical about it all. I find also that with that 7lb I can still fit into my size 10 jeans, I still have a BMI of under 25 and still look and feel slim. So it's a boundary for me, but not too strict that I can't keep to it.
3. I try to limit my carbs. They are my trigger foods and just make me want to eat more of everything else. As soon as I put on weight, I know it's due to carbs and immediately cut them out and can see the weight come back off again almost immediately.
4. I keep reminding myself of how much I enjoy being slim. I revel in it. I look at pictures of me, like at my Christmas night out etc and just keep marveling at the fact that I look so good. It keeps me motivated to stay this way. We've all said we don't want to go back to being fat, but just need to constantly remind ourselves of what it is we do want....to stay slim!
5. Exercise, I try to do something most days. The weeks running up to Christmas meant there was very little done but it's important to keep it going. Find something you like and enjoy. If you like it you will more likely continue. I've found a passion for running, and it's easy to do. No need for gym membership so it's free.