Change Credit Rating

I need to know the most effective and the fastest way that I can change my credit rating. I have heard that your credit rating number has to be constantly high for about 6 months before you can get a good rate on a loan. I know that my score has fluctuated a lot in the last 4 years and I need help to get it back in the high 700’s and I would like to keep it there. Would debt consolidation be a good way to get the numbers back up? Or would it just lump my debt together and not change the score?