Make sure the apartment is affordable.
When renting an apartment make sure you can afford the monthly rent payments.
Don't go for the fanciest apartment if it is really out of your budget.
Don't pay anything until you've seen the apartment.
Beware that some renters will want to charge you a fee before allowing you to see the apartment. If they do then walk away as it's a red flag.
If they want to rent you an apartment sight unseen then that is another red flag that they're hiding something.
Know where the common walls are.
You should factor in how many shared walls you'll have and which ones those are. Is your bedroom wall the other side of your neighbor's living room? Or vice versa?
Ask about their pet policy.
Even if you don't plan on having pets it's nice to know what the policy is exactly.
Consider your commute to work.
Consider how far you will have to commute. Would it be cheaper to rent an expensive apartment closer to your work or would it be cheaper to rent a cheaper apartment and commute longer to your job?