Travel locally to reduce your carbon footprint. Places nearer to you will have less of a journey and travel time, hence will be less on your carbon footprint.
Pack light and pack eco-friendly things like reusable bottle, your own cutlery, reusable containers to pack food, menstrual cups, reusable razors and so on.
Consider using bicycles or shared public transport to travel around when you're at your destination. It will save you money, is good exercise and will be eco-friendly.
Try going for activities that benefit the environment or activities that donate/use their proceeds for the upkeep of the environment like beach clean ups.
Try to stay at places that are green and eco-friendly so you know your money is going to a good cause and your carbon footprint is reduced.