The more you experiment with classes in Titanfall, the better you'll be able to perform. While the three default classes have a lot to offer, custom classes will let you best cater to your own strengths.
The first thing you'll need to keep in mind is that custom classes won't unlock until you get to level 5. That may sound like it'll take a while to get to, but the truth is that you should be able to unlock them with about two hours of continuous play--maybe even less than that. Once you do, you'll have access to a certain number of tools to choose from, ranging from weapons to tactical abilities to kits. There's plenty to look over here, so let's look at what each of the general classes have to offer, and what's bound to be best for you.
This is your main firearm, which you'll use over the course of the game except when you utilize a Burn Card for a one-time swap-out during a round. With the three default classes--Rifleman, Assassin and CQB--you'll have three main weapons to choose from, although more can be unlocked over the course of play.
The Rifleman's R-101C Carbine is a good general assault rifle, which has both distance and accuracy going for it, as well as a solid rate of fire. It doesn't have the spread of the shotgun, nor the lock-on capability of the smart pistol, but it is effective when it comes to mowing down ground troops or Grunts.
The Smart Pistol, the primary weapon of the assassin, is a great up-close weapon when it comes to nailing enemies with quick shots. They don't even need to be aiming primarily at them, as long as the lock-ons are in place. It usually takes three to bring down a soldier, so make sure you get these before you waste bullets.
Finally, the CQB Pilot's EVA-8 Shotgun is excellent when it comes to killing enemies quickly. What it lacks in range, it more than makes up in firepower, as it can bring down most ground troops with one singular shot, depending how much of the blast they absorb. Use these when you're taking care of groups of Minions, or want to get a surprise on someone around a corner.
Many people will swear up and down about the R-101C Carbine for general assault, but the EVA-8 Shotgun is remarkable, and fires at a pretty fast pace. The Smart Pistol can also do some good during skirmishes, although you'll really need to put yourself out there when it comes to targeting. Use it if you think you can handle it.
The sidearm isn't as vital as the primary weapon, as you're only likely to use it when you run low on ammunition. You'll start out with two selections at first- the Hammond P2011 (which both the Rifleman and CQB carry) and the RE-45 Autopistol. The Hammond is quicker on firing and reloading, but the RE-45 packs more of a punch because, well, it's a .45. If you have to choose one, go with that one, and then switch back if you prefer it.
Here's a weapon that's going to have some punch to it when it comes to taking the war to the Titans while you're on foot, unless you're gutsy enough to hop on and try to shoot out its core, that is.
The Rifleman has the Archer Heavy Rocket, which takes a few seconds to lock onto a target, but then fires a very effective homing missile, provided the enemy doesn't roam out of range.
The Sidewinder AT-SMR is the Assassin's token Anti-Titan Weapon, firing a string of rapid micro-missiles at its intended target. If they hit, they can be quite effective, but they don't lock on like the Archer does. The CQB carries the Sidewinder as well.
So what's more effective? It all depends if you prefer quick rapid-fire power or one smooth, lock-on shot. Aggressive types will want use the rockets, while more tactical players will prefer the lock-on. Try out both and see what works best for your class of soldier.
There are only two general Tactical Abilities that can be used with soldiers- Stim, which picks up a player's speed and movement, and Cloak, which turns them invisible for several seconds, making them undetectable to most soldiers on the battlefield.
Some may say that the Stim is a great ability for getting around, and in some cases, that's the case. However, for the most part, the Cloak is a better bet, especially if you're trying to get a jump on an enemy's holding point. Try out both, but chances are you'll probably come back to the Cloak.
As you become more accustomed to your weapons, you'll be able to unlock new attachments to help improve your performance. These include Iron Sights, for better aiming; Extended Magazine for higher ammunition count between reloads; and Suppressor, which makes your rate of fire silent, so enemies can't so easily detect you.
In these cases, it all depends on what you're accustomed to, but the Extended Magazine and Suppressor are best bets.
In most cases, you'll choose between the Arc Grenade and the Frag Grenade. The Arc Grenade does let off a big bang, but the Frag Grenade is way more effective. Stay with the classics in this case.
When it comes to Kits, you have a number of tools you can mix and match between the two that you carry.
In Kit 1, you have the Rifleman's Explosives Pack, which comes with extra pilot ordinance; the Assassin's Power Cell, which recharges your Cloak or Stim much faster; and the Enhanced Parkour Kit, extending wall running and hanging.
With Kit 2, you have the Dome-Shield Battery, which makes it last longer; and the Minion Detector, which reveals all AI soldiers on the map.
When it comes to custom kits, it's a matter of what you're comfortable with. In Kit 2, however, the Minion Detector is a solid bet, as it can help you bump up kills in a hurry- provided real opponents aren't around. Back to Kit 1, the Power Cell is probably the best way to go, as it'll let you Cloak a lot faster- an ability that could give you the advantage at taking back the battle. The Enhanced Parkour Kit isn't bad either, if you prefer to get to high ground right away.
Play around with all these options, and see what classes are right for you. No matter what you're packing, though, you'll be ready for battle.