Fastest way to get my credit score to go up

[nrdalert]

I was using Credit Karma up until about 2 weeks ago when I found out the scores are not FICO scores. I was pretty shocked when my CK score was 735 and my FICO score was 647. I'm trying to purchase a house and am waiting to pull my credit report until I see my credit bounce back a bit. Is it possible to get to 740 from here?

As of last month, I paid down a $2300 credit card (only card I have) to $500 and only have a line of credit with my bank for a small car loan. 
Thanks to life circumstances, a final bill didn't make it to my new address for a cell phone plan and it went straight to collections.  Because I thought I was being responsible in paying it off - I paid it in full, only to realize that blemish doesn't come off unless you negotiate with the Collection Agency.

What other steps can I take? I'm going to pay off the rest of that credit balance as I can in the next month or so. The car loan goes through next year - then I'm debt free. But my fico score is in the toilet. How can I make sure I get the best mortage possible if the only thing I can do is seemingly wait.

Any thoughts?

[takeshi74]

Keep in mind that even with FICO there isn'st just one scoring model and the specific scoring model used has an impact on the score generated.  See also the Understanding FICO Scoring Subforum and its stickies.

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@nrdalert wrote:

I'm trying to purchase a house and am waiting to pull my credit report until I see my credit bounce back a bit. Is it possible to get to 740 from here?

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Mortgage lenders typically do not use the more common FICO 8.  myFICO does provide mortgage scores but access is more limited to them.

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@nrdalert wrote:

What other steps can I take?

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If you want to see improvements then tackling the bigger factors first would be the recommended approach.

http://www.myfico.com/crediteducation/whatsinyourscore.aspx

Carefully research and see what you can do about that paid collection and any other derogs that you might have.  Make use of the Rebuilding subforum and other credit rebuilding resources.  You ideally want 0 derogs and 100% Payment History on your reports.