I have generally struggled getting a feel for any particular COD weapon, so the idea of custom classes has always appealed to me. However I never manage to settle on just a couple of classes (as I know some people do) and end up prestiging just to increase the number of slots open to me.
(I should point out I have only gone prestige twice on BO because of the effort taken to unlock the various challenges).

Since CoD4 I have generally ended up with at least three different custom class types; one for longer range combat (using burst or semi-auto assault rifles) for the large open maps, one for close quarters combat (using SMGs) on the smaller maps and a catch-all for everything else using automatic assault rifles.
If possible I then also have a "stealth" variant for the latter two, equipped with Ghost to counter the UAVs and spy planes.

As for perks, Perk 1 is either Hardline or Ghost (I did have a Scavenger because it seemed fun, but it isn't that useful overall unless you spit bullets like a lunatic or want to spam grenades).
Perk 2 is generally Warlord, Sleight of Hand or Steady Aim (for the CQB classes).
Perk 3 is generally Ninja or Hacker (because being able to booby trap a crate with Hacker Pro is just so much fun!).

What about other people? Do you use the custom classes much? Do you get by with just a couple and use them all the time or do you like to chop and change?

i don't understand why people have so many different classes...i got 3 different ones, 1 for assault, 1 for smg, 1 for stealth thats its. i prefer scavenger to ghost because i usually run out of ammo shooting people.
assault
Weapon: AK 47
perk1: scav
perk2:soh
perk3:ninja

smg
Weapon: Ak 74u
perk1:scav
perk2:soh
perk3: marathon

stealth
Weapon: Ak 47
perk1:ghost
perk2:soh
perk3:ninja

i use the same class all the time im sad like that

Galil/commando/AK47 (i prestige a lot so its what i have unlocked or feel like) with a red dot

perk1:Hardline (i know im nooby it gets me kills )
perk2:Sleight of hand
perk3: marathon

thats it playing in a pub environment that's all i need but in competitive play i use ghost not hardline

I have different classes because I like to vary the weapons, rather than just have a single weapon for all occasions (also not helped by the fact that my performance with a weapon can greatly vary from day to day).

I did start CoD:BO with "themed" classes, the only one of which that has survived is my main assault class
(Famas + flamethrower, China Lake, Hardline/Sleight of hand/Hacker). The others have reverted back to the Long range/Mid range and Close range classes I ended up with for CoD4 and CoD:WaW.

As I said above, I like the idea of a Scavenger class but I don't find it that useful when I can just pick up a gun someone else has dropped.

Assault class , aug with extended mags

Ghost or flak jacket
soh
marathon

Sub machine gun class, ak74u rapid fire

flak jacket
steady aim
tactical mask

Stealth class x 2 (winter and other camo), famas suppressed

ghost
soh
ninja

strella as secondary, frag,flash,jammer.

i change this all the time was trying the commando recently.Working out classes is a part of the game i enjoy a lot so'ive opened two extra slots by prestiging.

I have to have flak jacket and tac mask pro for almost every custom class. I love to run and gun.

Occassionally I will use my "scout" class inspired by tf2 which is:
any shotgun (i prefer spas)
cz pistol
any nades (prefer frags and flash)
any equip (prefer jammer)
lightweight
steady aim
marathon

loads of fun in close-range

Ive been using default classes for 8 prestige's now except the guns i pick up.

But playing on my mates computer now and again...

AK47
PYTHON
NADE
SMOKE
LIGHTWEIGHT
SLEIGHT OF HAND
MARATHON

Yeah ghee :>

sounds fun, I will try that one too

for me:

ak47/ak74u with dual mags
phyton/cz75/that stinger thing
frag and smoke/flash
jammer

preferred blue perks: scavenger, ghost or flak jacket.
preferred red perks: none really
preferred green perks: hacker or tacticl mask (with pro of course, fcking stuns)