But hey, I believe that new players would need all the tips they could get and these tips I give, although as far as credibility goes is pretty sketchy(well, I'm still using Trial mechs) are still tips that could be pretty useful.
I'll post whatever tips comes into my mind for now, I'll add later If I learn something new :)
1. Group Up
When the match starts, walk with other mechs, if you're using light mechs run forward and spot targets for the LRM and try to confuse the enemy. Don't try to be a hero unless there's only one enemy mech and run back to your team's brawler mechs if you're outnumbered.
For LRM Boats without any lasers, stay close to at least another mech that can handle incoming enemy mechs. For brawlers, go with other brawlers and focus fire on enemies. If you're using voice chat call out targets so that your lancemate knows who to shoot.
2. Group Up your Weapon
Shooting all weapons at once regardless of range is a bad thing to do and ineficcient in terms of heat management. Group your weapons by range or functionality and use them accordingly. LRMs won't work under 200m so stop shooting LRMs at close range. Turn off Small lasers on long range combat and only turn them on when you got close. Remember that lasers can still damage enemies until almost twice it's range but there is a damage reduction. The optimal range is the one written on your UI.
3. Dodging LRM
If you're constantly being rained death by the enemy LRMs just get behind cover and power down your mech(press P) this will break any lock the enemy team has on you. Make sure you're in a safe area with more friends than enemies though. In case you're in close combat with the enemy while being rained death try to get behind cover(hills, buildings, bigger enemy mechs). Those LRMs hurts so much that it is sometimes better to endure some laser shots than having to endure LRM blasts to your mech.
4. Open Grounds is never your friend
When you're marching with other mechs, try to go through areas with plenty of cover. Don't go for the open ground, even if you think you'll get a better shot. It'll be raining LRMs before you can even see where the enemy team is.
5. Capture/Defend Base
If you know that the enemy team are in the middle of the battlefield, try to ninja-cap their base, especially if you're using faster mechs. Most PUGS won't defend their base and ninja-capping will definitely give them some surprise. Even if they went back and defend, you've just successfully pull some of their fighters from the frontline and help out your team's brawlers.
On the other hand, remember to defend your base. Remember that jenner/commando that walked pass you at the start of the match? If you didn't kill them and they're not anywhere near the battle, chances are they're trying to capture the base.
6. Manage Heat
Watch your heat when in combat. If you're constantly overheating it's either because you don't setup weapon groups and constantly just spamming all weapons like an idiot or your mech is inefficient. Try to group up your weapon so that it's more efficient or add more heatsinks to your mech.
Well, I suppose that's it for now. I'll add more when I have a couple hundred more games under my belt :)
For those who are still confused on building your own mech, try it out with this program over here.
Thanks for Clan Widow Maker for making this useful tool.