If you want tips to level up just seriously play CQ LG (pref. operation lockers / flood zone) and use any class you're comfy with (really anything except Recon). Make sure the weapon has fast RPM, you can't really get away with low-fire-rate weapons in BF4 like you could in BF3 (unless I'm doing something wrong). ALWAYS use XP boosts holy forget I cannot say this enough. I'm level 60 in just like a couple days of playing, and I've gotten 5 service stars on both Engineer and Assault. Cap ALL flags and just get kills along the way, don't set out to have your main priority as getting kills.
It's magical.