Hi
May I say I bought MOO 1+2 and absolutely love number 1! It's simplicity is its real charm!
I'm wondering, is there a proper way you can declare war in the game (MOO1)?

yeah...attack

What I like to do before declaring war on someone is trying to get something out of it before spreading madness in their planets. I spy on them and check their techs, allies and enemies, and if something is interesting then I go to status and check both mine and their strengths. After that if I feel strong I'll threaten them and they sometimes offer me that tech and I will hold off the attack just to see if another tech pops up that I like. If they don't give in is time to espionage and conquer :D.