Try and figure out what feel good and where the problem points are. Remember, if the skate doesn't fit well after you are in it for 5 minutes in the store, they sure as heck aren't going to feel very nice after you have been on them an hour. Many stores offer skates for rent. If your perspective skate is available, use it. Frequently they also apply rental charges toward purchases so you have nothing to lose.
Skate parts are also an essential part of a purchase.
Metal bearing spacers are also very important for speed and stability. The wheels that generally come with most skates are crummy, so don't stress too much about them. But don't go dropping any extra money on wheels. By the time you need to buy new ones, you will know how you skate and can get wheels that best suit your style. Welp, thats it for now.