no one is probably going to through out a response to this question with out a little more info.. since every car is a little bit different before this question can be answered we will need to know what kind of car your running..
as for the center shock it is also different from car to car but in addition to that you can use it as a tuning tool. they say the further towards the front of the car the shock is mounted the more your car will turn.. to be honest with you i havent noticed that but i havent messed with it all that much. i just always put my shock in the furthest holes back towards the rear of the car...
When using side shocks you remove the tweak screws in the T-plate. All the tweak is adjusted with the side shock collars. If you are just using the side shocks as dapeners then you don't run the springs on them. I would suggest removing the tweak screws & using the springs.
The main thing when putting side shocks on a car is to make sure that you set the length on each shock correctly. To do this you will build each shock with the desired oil, mount the shocks to the car without springs on them & without the rear axle in the car. Set the chassis flat on a table making sure that the pod is setting flat on the table as well. Then measure the distance between the end cap on the shock & the body (see attached PDF) where it will bottom out. You want this to measure .170" or 4.3mm. To achieve this measurement, remove the ball cups & shave the ammount needed off of them. If you cut too much, just unthread them a little on the shock until you hit the correct measurement. After you have it set correctly either mark your shocks left & right or make sure that you only remove them one at a time so to never get them mixed up. Let me know if you have any questions, I'll do my best to answer them.