The more contact you have with players the better. Even if it's not always battle plans keeping in touch will help increase your trust and decrease the chance they'll attack you. However, to keep a good alliance it is best to make plans with your allies and attack others. This keeps you in contact it also makes your ally feel he's gaining something from the exchange. Also, talk to everyone, even those across the map, because if your doing well enough you should border everyone in the map.
My faith has found a resting place,
Not in device or creed;
I trust the ever-living One,
His wounds for me shall plead.
I need no other argument,
I need no other plea,
It is enough that Jesus died,
And that He died for me.