The first thing you need to know is that the techniques vary slightly depending on what type of central line you are drawing from.
For example PICC lines do not work with vacutainers - you must use a syringe.
Flushing differs with each type of line as well as the amounts of saline will vary and if you use heparin - that amount may vary for different lines - Groshongs don't use heparin at all.
The manner in which blood is drawn is something the hospital you do clinicals in will have spelled out very clearly in the policy and procedure. If you want to score points with your instructors go to the hospital and look it up - then you can use the P&P from your clinical site as your reference!
My hospital has two types of blood drawing techniques. One is the syringe method. ( based on a hickman) - assuming the line isn't in use and is clamped.
First you will clean the end of the line (we have clave tips) with alcohol. I ,rather than holding it up, open a sterile 4x4 to let it rest on while it dries. I can do others things while it is drying. I arrange syringes and label the waste one with a sticker or something so it dosen't get mixed up.
The amount of blood you will need will depend on the tests being run. Lets say you need just a CBC - so you need a small blue tube about 3 -5cc.
I have found that I like to use the 4x4 to hold the clave - it is certainly cleaner, so I grasp it in one hand and attach the waste syringe (5cc) with the other hand. With the clave system the tip of the syringe is removed and the syringe attached with a twisting motion. Unclamp the line, and gently pull back on the syringe. Ta da blood. Keep pulling back - when it is full, carefully untwist the syringe and set aside. If you only need a CBC, attach another 5cc syringe and pull back until you have the desired amount of blood. Remove syringe, and attach your 10cc flush pushing it in with a stop start type motion - this help clean out the line better than pushing in smooothly. Each hospital has different transfer systems for getting blood from syringes into blood tubes - so check.
A second method is to use a vacutainer system. These are usually in two pieces. One piece is small, narrow and goes into the hole of the vacutainer so the longer end sticks out. There is a cover to remove first. Have someone show you this! The longer end also has a cover the end of which you insert (after removing the cover) - not too hard they can get stuck - into the end of the hickman after you have cleaned with alcohol and let dry. Sticking out in the center of the vacutainer is a small black sharp ended device - do not try to touch it - it is a rubber covered needle! Once you have it in place unclamp the line and push your waste tube on to it - say a 7cc tube which you have of course labled as your waste. It fills with blood and will stop when it is full. Pull off, put on your blood tube for the lab to be drawn, then remove the vacutainer and flush following the protocol in your hospital.
Giving medications via a central line depends a great deal on what is going through the line - due to compatability issues. If you don't know if the drug you are pushing is compatable with whatever is infusing there are several ways to deal with it. One method is to stop the infusion, bend the tubing back at the injection port so it blocks leakage, flush with 10 cc saline, give drug, and flush agin after. Obvioulsy you need to be careful with the speed in which you do these pushes! Don't do this with blood or platelets.
The other choice would be to stop the infusion, disconnect the line and push the drug directly into the line, flushing before and after, before reconnecting.
The third choice is if you have a second line say a double lumen use the last method. My unit is a stem cell transplant unit and we don't use heparin while they are inpatient so flushing a line that isn't in use isn't an issue as there isn't heparin instilled.
This is a rather longwinded answer, hope it helps - I really suggest you go in and read or make a copy of the hospital's P&P though as everyplace is a bit different.