Setup trust

How do you setup a trust between two networks with 192.168.1.0 & 192.168.4.0 subnets. Do I need to have the same administrative accounts on each or what. What is the step by step particulars.

Both the subnets have their own AD. I need to trust these DomainA.com and DomainB.com .
I can ping by IP and name from domainA.com DC to
domainB.com DC but I can only ping by ip from domainB.com DC to DomainA.com DC.

Anyway, any help and suggestions are most welcome.

Thanks,