There are several different considerations to make when selecting hops. 

1. First, what beer are you trying to make?
   Many traditional styles like Czech Pilsner, German beers and English style beers require specific hops to be used, which makes the choice easier.
   For non-traditional styles then look for hops with the flavours and aromas that will enhance the beer, eg a tropical fruit-forward hop for a NEIPA. 
2. Next is to make a choice based on when the hops need to be added for bittering additions typically it is best to look for varieties with a high alpha low cohumulone concentration, this gets a gives a high IBU for the amount of hops added and the low cohumulone is said to give a more pleasant and not so harsh bitterness. 
3. Then lastly, look at what hops work well together, by looking at the flavours and aroma that each hop variety can contribute if they have complementary flavours. 

Read here for more information about hope types and their Aroma/Flavour.

Read about when to add hops and how that makes a difference.