When going about trying to fix your credit, keep in mind that not all credit is the same. Usually nothing positive comes from having consumer debt attached to your name. It doesn't even matter if you use it responsibly and pay it off on time, as it still doesn't look good to FICO, and it will look downright awful if you end up abusing it. That doesn't mean that you can not use it on occasion, but if you are trying to fix your credit scores, you need to keep in mind the affect this kind of credit will have on your score.
Everything from store cards, loans at electronic and furniture stores to credit lines with catalogs and personal credit lines with a non banking company is considered consumer debt. There are several reasons to take on this kind of debt such as various discounts and no interest payments for a certain length of time, which can sometimes be favorable and allow you to save money. The trick is to know how consumer debt affects your credit report and to help minimize the impact it has.
The Fair Isaac process for scoring has a bias not in favor of consumer credit for a couple of reasons, including being more costly and it is made up of things that FICO concludes raises the risk for potentially defaulting on a loan. As mentioned earlier, this kind of debt is convenient when used correctly but it usually doesn't end well for most people.
In order to be extra careful and really help your credit score recover, you can just avoid consumer debt in the first place. If you choose to use it, after you are able to use the store offer to your advantage, just make sure to pay the rest of the balance off. Do this as soon as possible otherwise, if you leave the balance on there too long, you will have ruined any progress you have made fixing your credit score.