I don't really think there is a best strategy. You have to play to your opponent's weaknesses. If they try to tech up right away, it probably means they spent little money on troops. In this case, rush them. A good idea is to try to keep the pressure on them. You want to dictate the style of game being played so they have to adapt to you. If you find yourself in a pressured situation, try focusing on gaining control of the situation. A small strike on something of importance to them could draw their attention away from your base just long enough for you to get some troops out there and gain control of the situation. Use unit matching. For example, if they bring in AT-AT's, don't attack them with Basic Infantry. You have to use something effective, such as Artillery, or Rocket Infantry. Don't lose control, and you probably won't end up in these kinds of situations to begin with.