Credit Score Management

I’m trying to boost my credit score as much as possible. I have credit cards but find it harder to get loans due to my score. I need help figuring out a sure-fire way to gain points by using the credit that is already available.

What are the vital points to be consider before starting credit repair?

I want to apply for an apartment but they need a 625 credit score. I lost my job for a few months and am now behind on two accounts.
My credit score is 597. I can bring the accounts current in less than three weeks but will just that be enough to raise my score those 28 points? I don’t want to waste my application fee just to get rejected.

I need to improve my credit score by 4 points for a loan. Is there anyway to quickly improve your credit score over a few weeks\months?
If I pay off the remainder of some of my student loans could my credit score jump immediately?

What are the vital points to be consider before starting credit repair business?