Getting fast XP in Battlefield 4 - best game mode and maps for leveling up

In BF3 you could play the Metro map as support or assault and level up fairly fast (1-2 games per level in the early levels).

Is there an good map/game mode for leveling up quickly in Battlefield 4?

The best/fastest/easiest way is, as Lyrion mentioned in a comment, to play on a capture-only server. This will give you a few thousands exp/minute, depending how good the people on the server communicate/play.

Example(16 vs. 16):

• 2 guys(1 per team) are capturing one point(or two), because they want some privacy or whatever
• Out of 15 vs 15 remaining, 7 on each side are afk and they left their soldiers at points A and B respectively. So there are only 8 people running per team. So at one side the capture will take a very long time(7 "defenders" and 8 "attackers" - same rate as if there would only be 1 attacker), and by the time teams will capture the points and run back, the flag will probably get neutralized before anyone of the team can make their way to it.
• That's pretty much the worst case scenario

So here's the best case scenario:

• Nobody is AFK
• Everybody runs as a group
• You only capture 2 points(A and B for example)
• Squad leader constantly gives orders to attack next flag

In this case you would earn a few thousands exp/minute

First, make sure you are using the bonus XP that you get from battlepacks.

The best way to level up is to play as a squad, follow orders, give orders if you're squad leader, drop medkits, ammo boxes, revive, repair, etc. You will get bonus points if you're performing these actions on or in vicinity of squad mates.

Points are what you need to level up and kills do not necessarily equate to points.

I find that I tend to earn the most points playing in Obliteration or Conquest.

However, when I want to unlock attachments for guns (which requires more kills) I will gravitate towards Domination mode.

Operation Locker is 'the new' Metro.

With that being said, the original Operation Metro is coming to BF4 in an expansion patch.

Truly the fastest way is to find operation locker CQ large servers and to run only assault. Throw down med kits and revive players all game. You will have hundreds of med kit medals and upgrade your med class quickly so you can enjoy some of the other perks such as the grenade launchers if you look for kills. By far the fastest way is sitting in the back just reviving and healing your teammates. You can maintain your kd and your spm skyrockets.

Different unlocks/level ups

There are few options depending on what you want to level up. Note that for unlocking attachments for guns, you need kills with that specific gun. For unlocking new guns from same class, you need points scored with that gun class.

If it's good weapons that you are after, most of the best ones you can get via assignments. For example if you're at least level 10, just playing Metro you can get F2000 and Bulldog.

What to play to unlock what:

• Just soldier kit:
  • Play Conquest on Operation Locker with few people and run around capturing.
• Soldier and weapons:
  • Play Conquest on Metro 2014 (Second Assault DLC), you'll get gazillions of kills around point B. This will also help you get kills to get weapons unlocks. Don't forget to drop medkits, ammo packs or motion sensors around B to get tons of extra XP.
  • If you don't have Premium, play Rush on Operation Locker. There are numerous choke points, where you can get lots of kills.
• Vehicles (except jets):
  • Play Conquest Large server, which is intended for 64 players, but only 4 (including you) are connected, drive/fly around the map capturing.
• Stealth jets:
  • Play Air Superiority (China Rising DLC), don't bother with kills, just go for capturing. Expect, that this will ruin your K/D though.
• Attack jet:
  • There isn't really straight forward way, IMHO the easiest is to use it on Conquest Large on Paracel Storm and keep going after the boats, helis and gunship. If you're lucky you can get 4 kills just by destroying one vehicle.

General tips

Use XP boosts, you will get more of them from battlepacks as you progress. Keep in mind that in BF4 XP boosts also the points that go toward unlocking specific thing. That was not the case in BF3, AFAIK.

Join biggest squad, with good players if possible. Stay close. You get much more points for helping them.