Hi
Suspension is the most important system in the car, it is responsible for how your car behave on the road. If you will design it well than you will stay on the road, if you won't you will loose control of your car on the first bend. If you are serious about designing suspension than you have a lot to learn and you should take it seriously. Luckily for you there are plenty of informations on the net.
First thing you need to learn is what is "suspension geometry"
It is very dificult to get it right because when you change one thing it affects everything else.
Second thing is type of suspension. There are few to choose from, double wishbone (double A-arm) suspension and macpherson strut are the most popular. Double wishbone setup takes more room, is more difficult to setup and it is more expensive but offer more control. You could say that macpherson strut is the opposite of double wishbone, takes less space, it is easier to set up, it is inexpensive, but it offer less control. If you want to design sports car you would choose double wishbone (or multilink if you advanced), if design every day car you would go for macpherson strut.
Third thing you need to do before you start designing is to establish how much space you have and you need to know dimensions of components you gonna use.
You don't design suspension you want, you design suspension that components allows you to.
Piece of advice don't believe everything you gonna learn on the web. E.g. some people (on youtube) build vehicles with double wishbone suspension and equal length upper and lower arms and claim handling of their vehicles is good. Don't believe that.
When you choose type of suspension and components there is something you can play with to check your setup: http://vsusp.com
