Eat more regular small meals. This helps speed up your metabolism.
Work out, and remember, to more muscle you have, the more calories your body burns at rest. Also more calories burned after exercising at rest.
Eat filling whole foods. Fruits, veg, wholemeal foods etc. Be smart with what you eat and avoid empty calories.
I find making changes that you're okay with keeping for a long time/permanently and slow steady progress is the best.