I have been doing a lot of research for the Cod Blops 2 Zombies ranking system . First i will start with the tally marks because everyone wonders what's up with those things some days you have 3;4 and maybe 5. The tally marks have nothing to do with leveling up rank wise tally marks appear depending on how much you play zombies.If you play zombies for one day this will result in one tally mark toward your current rank. If you play zombies every day (the time limit doesn't matter) you will see that your tally marks increase to 5...if you play zombies consecutively for 5 days.If you don't play at all you will loose tally marks depending on how long you don't play zombies.So for an example (and you can test this yourself) if you play Zombies for 4 Days for about one hour a day you will recive 4 tally marks but lets say you get lazy and you don't play for 3 days when you log back on you will have one tally mark maybe two if you start playing before the end of the day. The marks have nothing to do with the actual ranking system.The way the ranking system works is depending on your Kills to Down ratio nothing else matters but it dose look good on the leader board when you have more revives as a friend or have a really high distance traveled.
The ratio is
Dual Bones: 5 - 20
Skull 20+ K/D
Skull + Knife 80-100 K/D
Skull + Dual Shotguns 180-200 K/D
Now you might say WOW w8 a second your saying if I have 200 kills and 0 downs you will be max rank and sorry to say but that's not true each rank has a certain number of kills needed to receive it then divide by your K/D so in Zombies I have around 99 Downs and 20000 kills and I have a skull and a knife and I have never had 5 tally marks I only play on the weekends so the most I ever have is 3 tally marks.What tally marks do is you can see how many days the person plays zombies if they have 5 that means even if there not the best rank they play zombies almost every day so there not rusty,If you run into a guy with max rank and 1 tally mark that means he doesn't play to often but he's a good teammate. I saw on of the reply's it said my friend got 600 kills in a game and 0 downs and he ranked up the reason it the 600 kills ranked him up and he had no downs to affect his K/D so in his overall score it leveled him up I have done quite a lot of research on this topic and this is a video that explains the ranking system I posted above.
Bottom line is just cut your losses and don't be reckless when trying to get a power up or reviving a down team mate.I play alot of single player and that also helps when it comes to ranking up.Also what I originally tried to do is balance out my revives with downs it doesnt effect your rank.
And if you want to rank up in matchmaking play lots of Hardpoint.