Any ways of improving my credit rating quickly?

When I was 18 i took out A Credit card and only used it a few times but then foirgot to pay it off so it has screwd up my credit rating now i1m 22. I have seen some things for sale on ebay that say that they can improve your credit rating instantly. Do they work? Is there an alternative?
I don’t currently have any more Credit Cards as have paid them off. The only thing I’ve got is my student overdraft. So is there any thing else I can do?

Unfortunately, this isn’t a Staples commercial, and there’s no “easy button” to improve your credit quickly. 15% of your score depends on how long you’ve been establishing credit, meaning that it can take a lifetime to build it up, and blink of an eye to ruin it.

S&P Downgrades US Credit Rating From AAA

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