Option 1: Knife/Pistol Servers
There are many knife/pistol servers out there for starters. I earned the Veteran Knife Badge in one night, and the Veteran Pistol the next. Just remember to play as the medic to heal yourself and charge like hell. Once you have the timing down with the knife, it's a piece of cake. Aim for the head with the pistol or you will empty a clip in someone with no success. After some practice, you start to love using the knife/pistol over autos. (Just be careful of jackasses who stat-pad by using autos on Knive/Pistol servers, especially if no admin is keeping things clean.)
Option 2: For the Patient
Be patient and go "covert" while everyone else is charging head-first into the enemy. This was actually fun and you will learn new skills on sneaking up on people. Takes some time to get used to it, but it will teach you new tricks. Find staircases or rooftops close to the enemy, or hidden positions next to enemy flags and wait. Be ready to switch to auto if things go sour. Stay hidden and wait for the enemy to pass, then move in for the kill. Earned the Basic Knife Badge in this manner.
Option 3: For the Impatient
Play as a medic the entire map. Try to sneak around flags and hide, waiting for people to spawn and hit the dirt, then dive on them. Don't jab with the knife until you are on the ground and their body is right in front of you. For the pistol, same idea, except stay standing (or crouch), move in close, and pop them in the back of the head (to be safe, put two or three in the head for insurance) , then turn and rabbit, waiting for the next victim. Be careful if there is more than one, or you risk getting owned. Earned the Basic Pistol this way.
The bottom line is to get the timing down. If you must, work on Single Player to home in your skills. You can also time bunnyhoppers/dolphin divers once you get the hang of it.