When buying tickets and picking your seats, there are a few things to consider: the view, the atmosphere, and price. While the Emirates is one of the more American-style stadiums in England (this is the modern trend, as seen with the Man City’s Etihad, Sp*rs’ new monstrosity that replaced Shite Hart Lane, and others), the seating experience is different from American football stadiums.
One major difference is that home supporters and away supporters are kept completely separate: before matches, away supporters are not allowed in the same bars as home supporters, and in the stadium they are confined to a small area of the stadium that is barricaded by both physical concrete barriers as well as numerous stewards and police. At the Emirates, the away fans are always seated in one of the lower tier corners in the Clock End (see below).

East Stand and West Stand
The east and west stands are the sections that run along each side of the field. In an American Stadium, these might be the most desirable seats since they are closes to the middle of the field (“the 50 yard line”), but at the Emirates these are the seats with the least atmosphere and, in my opinion, are absolutely to be avoided. I sat here for my first match without knowing any better, and was disappointed with how quiet it was. Emirates is derisively mocked by other fans for being as quiet as a library, and there is some truth to that, but you can find a rowdy atmosphere if you sit in the right place.
North Bank and the Clock End
The North Bank is the section behind goal on one end of the stadium, opposite Clock End. As you might expect, it’s the section on the north end of the stadium that doesn’t have a giant clock in it. Clock End is the section on the south end of the stadium that does have a giant clock in it. Both the North Bank and the Clock End have the best atmosphere in the stadium, but the North Bank is all Arsenal supporters and you don’t have to contend with the away supporters. I personally prefer the North Bank for this reason, but it comes down to personal preference. For many matches, be prepared for the away supporters to be significantly louder than the home supporters, especially for Europa League matches and other less desirable opponents.

Upper Tier vs Lower Tier
This is another choice that comes down to personal preference. Assuming that you are sitting in one of the ends (see above), you will experience a better, louder chanting atmosphere in the upper tiers and also have a better view, but there is also something cool about being much closer to the field and seeing the players up close if you sit in the lower tier. I almost always opt for the upper tier, for the reasons mentioned above.
Club Level / Hospitality
As covered in my post on how to get tickets, if you simply can’t get a traditional ticket to the match that you want to go to, you can look into hospitality tickets. These tickets are significantly more expensive than traditional tickets and give you a luxury box atmosphere with catered food and drink. It’s a very different experience from the traditional Arsenal match day, and frankly not one that I would recommend if you’re a first time visitor looking to experience English football.