Pay which houses down first?

[Andy Wu]

I have both first and second mortgage of my primary home. The second mortgage rate is much higher than first.

I also have several rentals which have either 15 year or 30 year loans, they have different interest rates.

If I want to pay down the balance, which loan should I pay down first, and what's next? 

My guess is to pay down the second mortgage of my primary home. Then I don't know what should I do. Will it be my primary home first mortgage or the highest rate of rental, or the loan with smallest balance.

I am paying minimum due for all loans now.