Okay, I'm still in the process of rebuilding my credit, but the all time low that I saw it hit was in the 420-430 range, from the high 720's...I honestly didn't watch it super close shortly after that as I knew it wouldn't bounce back right away, so it may have plunged lower at some point. Currently I'm in the 630 range and climbing...my point being, I've been there!
For me, it was caused by a divorce that I didn't handle very well (I should have counter filed with the help of a lawyer, which I was stupid enough not to do because I was "too broke - oh, how I've paid for that, quite literally). At the time, my minimum payments were still too much for me to handle - I literally did not make enough to cover them. Had I been able to do so, I would have at least paid minumims and put together a "debt snowball." But, that was impossible, even working two jobs, so I had to go through a debt consolication company - no one would look at me for a loan, so I was stuck between that or bankruptcy. I chose that route, knowing my scores would be horrible for awhile, but eventually I'd be able to recover, which I am.
If you can make your minimum payments - DO IT! At least keep them current from here on out, even if you can't make back payments. Call your creditors and explain that you will keep them current and see if they'll write off some of the fees and/or lower the minimum due. One of my student loans was very willing to work with me that way, which was a huge help....but you have to get on the phone and talk to them, escalating it to managers quite often, depends on the company.
From there, the debt snowball - I set up an excel sheet with my debts, entered the info in, and then sorted it first by lowest monthly payment, then by interest rate, then by lowest debt amount, and anything extra went to the first one on the list first...once that was paid off, the minimum from that PLUS any extra was added to the next one on the list. I have paid off several accounts this way!
A HUGE key is knowing where your money is going and when. There are online tools and apps but I found none of them that really did everything I wanted, so I built my own budget tracking spreadsheet with several pages in it. Page 1 is my monthly budget plan. Page 2 is my day-to-day tracker so I don't forget about an auto-payment or check someone is taking forever to cash (to avoid any "extra" fees which can REALLY kill your money each month!). I also have a section where I lay out my "set bills" several paychecks in advance so I can pre-plan how much I may (or may not) have available for spending in other areas. Page 3 is a monthly summary - for each entry in 2, there's a drop down category menu - each month I tally each category (super simple with a filter) and see if I'm at, over or under my budget. This allows me to plan better and budget better. For example, do I run over my food budget every single month for several months in a row? Then I either need to make a drastic change or adjust my budget accordingly. The final Page 4 is my debt snowball, anything new is entered and all I do is re-sort the data.
Gaining control of where my money was going and realizing what I was ACTUALLY spending has been HUGE in me improving my credit - in fact, it would not be where it is without it. I've passed my tracker on to a couple of friends and it has worked great for them as well. Another very helpful thing you can do is set up auto-payments or use your bank's Bill Pay if they have one. I prefer the bill pay as I can control a little better when a payment is made, but it still sends me reminders and I can schedule them to pay automatically whenever I want them made. This way I'm no longer missing or forgetting a bill.
The Bill Pay and the budget tracker combined now have me in control of my money. I no longer have to bum $5 for gas to get to work because I ran out of money...and my credit score is rapidly growing as I pay down debt. It's a good feeling to feel in control of your money again - while it's not always "fun" or "happy" at least YOU'RE in control instead of it controlling you!
