Credit Karma is good tool for your srsenal, but only for a rough estimate of your score and utilization. A few years ago before they got super popular, they were much better. They used to let you get weekly pulls that were very close to TU. I used it about 5 years ago before getting a car loan and it was accurate to within a point. I've used it in the time since when doing loans and such and it's usually off by a whole lot. Like everyone else said, they use FAKO scores and can be anywhere from accurate to completely off depending on what real source you compare it against. Another issue is that they give only ONE score which does you no good if you're looking for accuracy since even the big 3 can vary a lot.
If you already have credit cards, you're much better off checking to see if any of those cards (Discover, Barclaycard, AmEx, etc.) give you a free score and use that in conjunction with CK to get a more realistic picture.
The best option out there (though paid) IMO is credit check total. It's from Exprian and gives you your score from all 3 bureaus (once a month from EQ and TU and daily from EX). It's $1 for a 9 day trial, then goes up to $29.99 a month if you don't cancel. When you call to cancel, they give you a %50 off "deal" for 5 years bringing it down to $14.99. To me that's excellent deal of you can afford it since it gives you all 3 bureaus with your real scores and updates you when things change similar to Credit Karma. If you compare the numbers side by side with CK, it's crazy how off CK can be sometimes.
As for forums, the MyFico forums is the absolute best for getting these kinds of questions and way more answered. They give tips on everything from how/when to apply for cards to have the least impact on your score (app spreeing), to how to fall back for a while to build your score up (gardening) to getting mad $$ for you credit activities (churning). It's full of good advice of how to learn about building and maintaining credit. People also post their credit growth and horror stories to help others avoid the same mistakes. They also put me up on additional ways to get free real credit scores through soft pulls from a few of the reputable peer to peer lending sites too.
