Hello!
I'd start by making your target weight on here a stone or so under your current weight. You can then amend it as you achieve it and so on and so forth. It can be motivating to see yourself close to a target as opposed to seeing '7 stone to lose ' for example and feeling disheartened.
Also set BMI goals and half stone targets. Dress sizes are another good idea and things such as wanting to fit into a specific dress or skirt.
Rewarding yourself is good too - however not with a bag of minstrels!
I went from 15 st 2 to 9 stone and mini goals helped a lot