Raising your credit score can take time and you certainly won't be able to get it raised a whole lot within 30 days.
But you can increase your credit score a little bit in 30 days by getting any errors corrected on your credit report by contacting the credit bureaus and disputing any errors that may be on your credit report.
Raising your available credit and making more than the minimum payments to your credit cards on time can help raise your credit score little by little.
Reducing your debt to income ratio can also help you raise your credit score but all the above will only raise your credit score a little bit in 30 days but to fully recover from a bad credit score and raise your credit score to A great credit score can take 5 to 8 years.
When you have collections placed on your credit rating the collections accounts along with negative information stay on your credit report for a period of 7 years before they drop off and stop affecting your credit rating.
However you can go through a credit repair agency to help remove negative remarks from your credit rating sooner but it will cost you money.
Best thing to do to raise your credit score is to be responsible with credit and keep making payments on time for loans and credit cards and stay current with even your utility bills because if you default on Utility bills those bills can be sent to collections as well and harm your credit score and then it will take another 7 years to get those remarks removed from your credit rating.