Since you've never flown, get to the airport 90-100 minutes before the flight. You don't need the stress of rushing to do things you've never done before. Go to the check in counter. Check your bag if you have a big bag. Otherwise, you can hand carry one carry-on bag and one smaller computer bag/purse/etc.
When you get your ticket, try to get an isle or window seat so you don't get stuck in the middle between two fat people... sorry to be so direct, but they'll hang over into your seat.
Make sure you don't have any prohibited items. There's a list at the airline's website. If you use the bag for other purposes, it's easy to forget something... like scissors, for example.
You'll need to put some items in a quart ziplock baggie. Do this before you leave home. You'll have to take your laptop out of the bag and put it in a separate bin to go through x-ray. All of this is explained with signs. Veterans will be rushing through this, but just take your time. This is the most confusing part, but parents with kids take forever to do this. Just ask someone if you don't know what to do.
Go to the gate. Before they call boarding, go to the bathroom one last time.