like they said alot depends on where your SA's are but I've noticed alot of people espically if they are green disclose their large country just to remove the risk of it getting ivnaded, and alot of people when playign either colour try and cover as many potentially hostile borders with lavs until they find out where enemies are. Red has the advantage of being able to maouver 1st so can get away with transports and tank/bots for invading, but once the enemy does break into one of ur sa's it's very ahrd to get him out again so covering borders is alqways a good thing in my book.
As for sea fights ask someone whoc an win them

i'm still trying to find some tactics for them.