I’m looking to pump up my credit score from 640-to 700 to get a better interest rate on my mortgage.

I’ve heard opening new credit card accounts can help (some say it could hurt) the score but i doubt that would be enough.
I surfed the internet and read about credit repair experts that could help. Has anyone tried these guys?

Do they really help and if they do how much can they help. The agency i talked to there name was Lexington,
but not sure if they can help as much as they say they can.

Agree about the credit repair companies.

It's not that hard tp build up your FICO. Over 1/3 of your score comes from payment history,
and just under 1/3 comes from proportion of balance to available credit.

So here is what you do :

Pay all of your existing credit cards down to less than 20% balance, pay them off if possible. If you cannot pay them off then continue to make payments of them (not the minimum) and stay under that 20%. If you can pay them off, DO NOT CANCEL THEM, with the exception of department store credit cards or any other type of consumer credit card (Best Buy, Office Max, etc.).

Now, let's say you have zero balance and 4 open cards. Use a different one every week to get something small that you would normally buy with cash, say a tank of gas. Pay each one off before the end of the billing cycle so as not to incur any interest charges. You are getting the benefit of the consistent payment history, with the benefit of low balance to available credit ratio, and it's not costing you any extra money to use those cards.

Keep that up for a while and your FICO scores will be up there with the best, the right way.

For those who don't know what a Credit Score is :

Not much useful for us Indians.

Personally I doubt that such credit repair experts do a good job; if it were so easy to fool the system, it could no longer be called reliable for credit ranking...