F1 is technically one class of racing but all the cars are NOT equal. If you split the field into three categories, top teams (Merc, Ferrari, RBR), mid field (Williams, Force India, etc) and back markers (McLaren, Sauber, etc) it becomes much more entertaining. Treat each like their own little sub race. Pick a team to root for from each level.
Second, if you are US based, Montreal is almost always terrific. Austin as well. I was at the 2011 Canadian GP and it was epic (Button went from last to first in torrential rain). Try to get a seat that is in a good overtaking area. This is something you may want to ask this thread depending on the track.
If you are watching on TV, try to finding a bootleg stream from the UK. Coverage is much better and there are no commercials during the race.
In terms of the racing... DRS and the hybrid engines are the big differences between other series. DRS is a little flap on the rear wing that reduces drag and increases straightline speed. During the race it can only be activated if you are within 1 second of the car in front AND WHEN you are in a specific part of the track, usually a straight. F1 is very aerodynamic dependant. Cars can't pass each other at will. This is why DRS exists. Pit strategy, tire wear, safety cars etc all play a big role as well. There are a lot of micro battles beyond just outright position.
For the drivers, Lewis Hamilton of Merc, Sebastian Vettel of Ferrari, and Fernando Alonso of McLaren are the three most talented drivers. The later is unfortunately on a shit team. This year is looking to be a Lewis vs Seb battle. With that said, it is entirely possible other drivers and even other teams put in a surprising performance. There is also usually a "punching bag driver" who is always shit or crashes a lot. In past years it has been Pastor Maldonado. This year it might be Lance Stroll. Expect humorous memes around this driver or any driver who does poorly.