If you are playing in Instant Action mode, choose the water terrain (the Road to). There is a bridge not far from the starting location.
Go to the bridge and hide under it. The enemy Mech AI will have trouble understanding this tactic. They will almost never come into the water to get you. They will often sit on bridge while you peek out from below and blow them to pieces. If done correctly, you can take out ten to fifteen waves (thirty to fourty Mechs) before you take significant damage. Since you are in the water most of the time, remember to take lots of lasers. they work well in the water and heat should not
be a problem.
After the Pirate missions are complete, you will arrive at the Canyan Ends in the middle of a island-like area. it is extremely difficult, and the only way to finish may be to be Dishonorable (enable the 'Invulnerable', 'No heat', and 'Unlimited ammo' options). You will face pirates and People on your own team on the Fed.Suns Missions.
To build the best Mech, arm any Mech with maximum armor, 5 ER Laser Large, then use the rest of your space on Double Heat Sinks (clan).
During a mission, switch your fire group to 'Group Fire'. Aim at any enemy and fire. This will do major damage, and after shutting-down and re-powering up, you are ready to repeat the process.
All powerful Elemental:
If you minimize an Elemental's engine and get rid of all of its armor, weapons, and equipment, you should have just enough tonnage to add one ER PPC.