Mech Configurations

When you fight on-line one of the main factors that contribute to a win or loss has to be the mech you take into battle. 
Consult the booklet that came with the game on how to use the mechlab.
Choosing the right mech for play is a skill you pick up as you go along. 

The main factors that you have to take into consideration are :

Stock Mechs - If you can only choose from the standard or "Stock" mechs then you can only choose from the standard variation's of the mechs that come with the game.  Picking the right variation is still difficult though.

You should try all the different stock mechs in an off-line "Instant Action" game to find one your comfortable with.  If you still can't decide ask your team mates in a game what mech you should take.. If you haven't got a favorite stock mech yet this maybe a way of finding it.

The Map - If the map is an standard map or custom map like an Ice map. 

If it is a standard map you can use any weapon the game allows as long as you can control the heat the weapons make.  Heat sinks are a must for a hot map.

The Ice maps take away the effect of heat.  If you can pack it on a mech and are allowed to take it - STICK IT ON!. 
(note..  to many lasers on a mech - group fired may still blow you up)
The main weapon for Ice maps are UAC 20's (Ultra Auto Cannons) as 2 of them can knock a mech over if you hit it dead on.

Unlimited ammo - If the game is U/A then the mech doesn't have to take Ammo.

When in the mech lab the 2 things that restrict what you can place on your mech are the weight  and criticals. You save both these if you don't have to place ammo on your mech.  This means more weapons for the weight of the mech.

Weight Limits  - If the host of the game has put a weight limit on the game it will cut your choice of mechs down.

Check the title and the info of the game for the hosts options.  There maybe a limit on how small or big the mechs have to be.

C0 to C7 codes - The codes that most people use on the zone show which weapons are allowed in that game.

C0 - Stock mechs only (no custom mechs)
C1 - Energy Only (Lasers)
C2 - Energy and Ballistics (Lasers and Guns) 
C3 - Ballistics and Missiles (No energy)
C4 - Missiles and Energy (No guns)
C5 - Ballistics/guns only
C6 - Anything Goes
C7 - Missiles only

Make sure you know what "C" the game you are in is..  then you can't get told off by the host for bringing the wrong weapons.
 

Team Mates - If you are playing a team game your mech has to compliment your team mates choices.  If its a stock game and your team mates taken a missile long range mech, you might want to take a short range laser mech.

To talk to your team while in the Mech3 launch bay you click on the "chat team" button.  this will only send messages to people that have joined up in your team.

Notice that it tells you which messages are to your team and which are sent to all players.  It will show this for your team mates too when they send you a team message.  If they send a team message don't forget to click the "Chat Team" button yourself to reply!

You'll find the mechs you like eventually.. I myself have only 5 mechs that I use that fit all the maps and C codes.  Took me a few months to find them though - Good luck