help with 2 providers (load balancing)

Hi,
I have pc with 3 lancards… eth1 and eth2 with internet provider and eth3 is to give internet to all my clients.
can you tell me what settings shuold i use..ip,gateway dns and etc. and how to set load balancing?
thanks!

Please check this http://wiki.mikrotik.com/wiki/Load_Balancing_over_Multiple_Gateways