I ruinned my credit about 10 years ago by going through debt consolidation thinking it was a more ethical thing than BK, I paid my discounted dept with hard earned cash and cbr scores that plummeted to the 500s! I bought a house with non-prime rates 9% 3/1 ARM!!! Exactly 3 years later I refinanced with credit scores close in the high 600s and got 5.125% fixed 30 yr.
This is how I did it:
First of all, paying my mortgage on time every month really helped, (and paying a little bit extra shows you are not in debt-to-income problems, even at that high interest rate) but even before my score showed promise I got a credit card (could only be approved for $300 limit then). I used it for gas and paid it off in full every month. One time I charged about 80% of my limit and they automatically raised me to $800 limit, but that was about 8 months after getting it and using it faithfully. Now that card is at $4000 limit, I have never asked for an increase, and I still pay it in full every month.
During my low credit score time I also got a student loan. I have paid that every month on time (the trick on this one is to pay more than the balance due. My bill is $10 a month and I pay $55.
Between paying off all cards every month, keeping my home equity loan at a reasonable balance and paying my mortgage ahead of time I now have close to 800 credit score. And I only use credit cards because I get Amazon dollars, Delta airline miles, free gift cards, plus my purchases are insured and if my cards are stolen I'm protected there as well.
BTW: I worked for a bank in the credit card department and learned what to do and what not to do with credit cards.
Here goes: If you have to revolve your balance (not pay off in full) never revolve a balance that is higher than half of your credit limit. So at Christmas time, you can get close to the top (80%), but the payment needs to be enough to bring it down to half or less. Never get so close to the top that you risk closing the month over your limit. this makes you high risk with the bank, causing your interest rate to shoot up to default that same month, it also brings down your credit score the following month when it is reported.
Never apply for more than 1 credit anything in 6 months, even better - 12 months. So if you apply for a credit increase, don't apply for another credit card for 6 months. Only apply for increases for a special purchase that you are going to pay off right away, anything else, let the cc company do it on their own; it doesn't hit your cbr as a derogatory, and it doesn't look like you are trying to over extend yourself.
You can't practice this on just one card, it has to be consistant with all revolving credit. CC companies use your cbr to view habits even after you have been paying them faithfully every month. If they see something that triggers their flags on your cbr like other cc with high balances, they can lower your limit and raise your interest rate in the same month which can end your month over the limit and lots of negative cbr stuff.
Now I have 12 credit cards - 6 Visa, 1 MC, all other store cards because I get special discounts, lowest limit $4000, only one Visa has a revolving balance because I used a 2.99 balance transfer offer which is at less than 50% of my limit and I pay at least $15 more than my amount due every month.
You can rebuild but you can't be impatient and you do have to pay the price in the meantime.
Thought I was doing pretty good getting my scores up but I guess not good enough for them.