Make preparations in advance. It's a good idea to make arrangements for your mail to be picked up, your plants to get watered and for pets to be taken care of.
Let a neighbour know. Choose a neighbour you trust and let them know you will be away on vacation. They may offer to help you with your mail and plants, and if they see or hear anything suspicious while you are away they can do something about it.
Empty the fridge. Depending on the length of your vacation, clean out your fridge and throw away leftovers and items that will expire. When grocery shopping leading up to your vacation, be aware of buying less so you don't have to throw as much away.
Get light timers. Set up a few light timers throughout your apartment and schedule them to turn on at certain times. This will give the impression that someone is at home while you are away.
Find the perfect temperature. Adjust the thermostat to a reasonable temperature. That way, you won't be wasting energy and there will be less of a risk of any potential fire hazards.
Turn everything off. Make sure the stove is off and unnecessary electronics and appliances are unplugged.
Lock up. Go through your apartment and make sure all windows and doors are closed and locked.
Have a great time! After you ensure your apartment is all taken care of, enjoy your vacation and RELAX!