When you spawn, do the usual thing and finish round one, while constructing the turbine. When the round is over, open up the two doors with the turbine, head on the bus and buy the B23R. Hang around the Depot (I usually look for some other pieces, occasionally I find the ladder for the bus there) until the bus hollers to leave. Get on board and go to the next area. When you arrive at the diner right away head down to the door that requires the turbine and grab the piece that's there. Normally it's the snow plow piece for the front of the bus.
Good so far, if you're lucky you'll get the hatch or the snow plow early on, and you can attach those pieces. When you're passing under the bridge between the depot and the diner, look to the wall near the M16 and check if the Wonder Weapon part is there. If it is, quickly jump off, grab it, and jump back on (or stay and buy the M16 if you want).
I'd recommend (if you get the hatch) putting it in the diner though, so you can grab the Galvaknuckles for 6000 points. They'll be very useful when fighting the denizens, the electric boss, and normal zombies (up to round 13, when they stop being a one-knife kill).
Build the piece if you can, then open up the door to the box ASAP and if you hit it once or twice with nothing solid, open the other door and get the MP5. You can either stick around there until the box moves, or keep going through the areas to grab some perks.
I would recommend staying for one (or more) revolutions of the bus until the box moves, that way the box will be in one of the next areas you move to. Also, what do you mean by "keep going through the areas to grab some perks"? You need to turn the power on first (unless that's what you meant). Also, go for one spin on the box and if you don't get something good, get the MP5. That's pretty good in this, and it's reliable (especially for ammo).
When you get to the Power area (where the AK74u is) it gets tricky. If you're fast, you'll have no problem, however. As quick as you can, open the outhouse door and hop down, and quickly assemble the power switch. Crank the power, and wait for the machine to do it's thing, and if you're lucky, the bus will still be there. If it is, hop on and head on to the Town to get your Juggernog. If it left, you're gonna have some problems. That area is particularly hard to hold out at, especially without Jugg.
I agree with this.
I often just try my luck with the Denizens and sprint there on foot, though that is risky and will often result in a down / death. If you're skilled and want to try it, go for it. Sprint as much as you can, and if you don't know, the Denizens (the things that jump on your head) will latch on to you and you have to rapidly melee to shake them. If you survive that, you should arrive at the town. Your primary focus should be getting Juggernog, and once that is obtained, the Town is a good spot to hold out a few rounds, or all game, really. Instead you could get on the bus again and head across the bridge, towards the bus depot. This is fairly simple, just survive long enough to get there. Once you arrive, it's just a matter of going through all the areas again and getting your perks.
After that you have some choices. You can either
a) Hold out at the Farm (my favourite, although probably the most challenging)
Problem here is ammo, but you have that shotgun you can buy off the wall (plus Claymores).
b) The diner is also a good spot, very open.
I'd say this is one of the best. You have the MP5 if you need ammo, or you can just run around shooting and stuff
c) The Town, which I consider the hardest because of all the lava.
Again, there's the issue of ammo. However, if the box is at the location you're staying at, then good for you.
If you go with the Farm, you can either do a simple train around the base of the big truck, or around it (the latter is more likely to get caught by a couple individual zombies).
On Survival I've done fairly well running around the truck in the centre of the farm (not sure how well it works in Tranzit). If you're getting trapped, you can escape into the barn or run upstairs in the house and jump out the window.
If you choose the diner, just do a train around the gas fill-up and by the box building. Then town has a multitude of options, such as making a stand in the box building (not recommended on solo), or training in the area near the stairs leading to the Juggernog house. The rest is up to connection and luck.