Which strategy (in-game strategies) to pick really depends on your taste. Some people like MoS, other SM. I personally like GW. So pick the one that you like the most (later on you'll learn which strategy to pick at which situation).
Tactics I'd say wall all your countries, attack enemy's major cities before reinforcements turns, if you use stealth attack from the back, and if you're playing a poor game try to get as much income as possible.