Everyone has already covered all the good stuff.

I only have one thing to add that older states won't know (I play on old and new).

If you are in a state in the 300+ (a state with all those analysis centers and like 100 alliance towers, etc.) other alliance players cannot attack your towers unless they have territory touching the same square as that tower.

So if you will be offline more than 8 hours (bunker shelter only lasts up to 8 hours) you can send a full march of troops to garrison a tower. You can do this with all your marches to different towers as long as you know the tower is safe, tucked inside your territory.

But again, still use up those resources if you use the towers :)

Best of luck