US Credit virgin

[paul]

Hi there,
I'm currently immigrating to the US from Canada and will be starting a fresh with my credit here. I did open a line of credit and Credit card with a US sister branch of my Canadian bank just to get the ball rolling. Options are extremely limited when you dont have a SSN yet.
I have a couple of questions about my situation:
1) Being as I've had these accounts for about 8 months and have had them at between 20-70% balance, once I get my SSN should I expect a fairly decent FICO score?
2) What is usually the optimal balance to run credit accounts at to achieve credit points fast?
3) Does anyone have any tips for someone in my situation? Time is of the essence for me because I would like to qualify for a mortgage by the end of the year.
Thanks
Paul