Honestly anything that you're comfortable with is good. Scavenger is good for grenade spamming, Warlord Pro as well. just pick classes that you know will help you get good killstreaks.

Oh and avoid Nuketown FFA like the plague. Also the best killstreak right now is the SAM turret. A lot of UAV's will be up and each destroy will give you minimum 300XP and help your team win.

Primary: AK47 (May be nooby but you get kills)
Secondary: AT4 (for taking aircraft down)
Perks:I really use the ones that I feel I need depending on the enemy team (eg.) Do they have good players, noobs or the usual 12 year old.
Killstreaks: Spy Plane, Blackbird and Chopper Gunner

Just use any gun you're comfortable with and use scavenger and sleight of hand for your first 2 perks

Do what every other noob on black ops does and camp with an ak74u or famas.

if your playing nuketown 24/7 then ak-74u with rapid fire, if not just use a good assault rifle with scavenger and go for choper gunner gunship etc, also HQ is probably the best gamemode for levelling, capturing hq will be like 500 xp per each one then 100 xp every 15 seconds or something.

(sorry for the essay)

Primary: Famas/dual mag
secondary: any pistols you want
Grenades: Semtex/concussion
Equipment: C4
Perks: Hardline/SOH/Hacker

Primary: Your Favorite assault rifle or stoner 63
secondary: RPG
Grenades: Semtex/Flash
Equipment: Claymore/C4
Perks:Flak Jacket/SOH/Tactical Mask PRO or marathon

Primary: 74u rapid fire/ or your favorite smg
secondary: Any pistol/ or balistic knife for fast knifing
Grenades:Semtex/Concussion
Equipment: C4
Perks: Scavenger/SOH/Marathon

Using warlord has been my best way to level up, I've been using the famas with extended mags and either silencer or red dot. I don't buy these attachments untill I'm ready to use them, this way you can do 2 attachment challenges at the same time giving you lots of xp. So I tend to stick to one gun, trying to hit those 10,000xp challenges.
I only use napalm, blackbird/rolling thunder, dogs/hind. But, I have also found that using SAM turrets are a good source of xp as there is often something flying around to be shot down. They can shoot down enemy care packages into a different location, bringing the enemy out seeking it. Alot of people use spy planes or counters, this will drop them fast.
Care packages are also good, you get xp for using it and then xp for using whatever it gives you, which could be a chopper etc.
I've used these kinda methods across multiple accounts, they work for me, try them and see what you think :y:

If you wanna really be a boss exp collector. Play demo,hq,dom and just keep getting sam turrets. During the last 2x exp. i played nuketown 24/7 and had sam turret, sr71,dogs. lmaoo 5 sam turrets up at a time? chopper gunners got shot down before they opened the door. even a spy plane kill is atleast 300exp. imagine how many there will be though since its THE most common killstreak in objective games.

Yea basically, If you cant beat 'em, join 'em. I'm guilty of being a famas noob right now but I'll use whatever works.... :embarrassed: