1. Travel Mid-Week
Traveling mid-week instead of on the weekends has two benefits: airports are less crowded (which means shorter lines) and the airfares are cheaper - these have both been proven to be true. The two cheapest days of the week to travel are Tuesdays and Wednesdays.
2. Remember What Carry-on Liquids You Can and Can't Take
This is important because you don't want your expensive face cream or bottle of wine to get thrown out. Here is what you are allowed to carry on: liquids, gels, aerosols, creams and pastes are restricted to 3.4 ounces (100ml) or less per container, and must be in a 1 quart-sized, clear, plastic zip-top bag.
3. Check-In Online and Print Your Boarding Pass
Most Airlines will allow you to check-in online 24 hours before your departure. It is always smarter to checkin online to avoid the long lines and to print your boarding pass, because even if you have your flight information in your email or you took a screenshot of it, you always run the chance of not being able to connect to wifi or of your phone dying.
4. Arrive At Least 2 Hours Early
This is also VERY IMPORTANT. 2 hours is the minimum amount you want to give yourself to get to the airport, check-in, go through security and find your gate. You never know how long the lines are going to be and depending on the size of the airport, your gate can be a tedious place to get to. The more time you give yourself, the better.
5. Set An Alarm So You Don't Miss Your Plane
As stupid as this sounds, I have come close plenty of times to already being in the airport, ready to go, but have a longer layover and end up roaming around and loosing track of time. It happens! Set an alarm! Better safe then sorry.
6. Make Use Of Your Dead Time
If you have a longer layover, you have a lot of time to kill. Take advantage of it! Walk around and explore the airport you are in and go look around the shops or try a new restaurant. Plus, you'll be sitting on a plane for the next few hours so its better to walk around then to just sit at your gate.