What strategies have you guys found that is good for the early game? I make land and sea exploration a top priority. Those artifacts and barbarian war spoils really give me leg up!

Depends on numerous factors;

• Civilization you're playing as
• Game type
• Whether you're aiming for a particular victory
• Difficulty level

simple. This will carry you through the entire game. Focus your resources on military and science. Keep peace as much as possible while you build your massive army and when you have an unstoppable force, attack and dominate every other civilization. 

I like to build up a strong defence before doing anything offensive. Of course if there is a weak civilization right next to me I will conquer it :)