1. It is not advisable to leave your aquarium lights on at all times for the aquarium. You should keep the lights on for 8-12 hour periods at a time. If you want to keep the tank lights on when you arrive home, simply get a timer for the lights so your fish stay on a schedule.
2. You should always thoroughly research the type of aquarium you are going to be setting up before you purchase it. Make sure you have the proper gallon capacity and shape that will fit in your home.
3. When starting out a new aquarium, it is best to add hardier species at first. Once your aquarium ages a bit and gets settled, you can start to add more sensitive fish to the aquarium.