How can I raise my credit score in 6 months????

I currently have a 596 credit score. I have one single debit card and one single credit card. I don't use the credit card too much and always pay it on time. However, I'm new to the country so I've only had this card for around an year. I really need to up my score until May because I'll need to rent an apartment by then. What are the quickest ways of doing that, and what would be considered a good credit score for renting a place and maybe picking up student loans as well?