D.C.
I am so sorry to hear about your miscarriage. Depending on how far along you were when you miscarried, some doctors will recommend that you wait 3 months before trying again. If you were miscarried very early in your pregnancy, then there is no need to wait. You should ask your doctor about this.
There is no way to try to concieve with twins. It happens on its own, or it doesn't. Your chances of having twins are higher if twins run in your mom's family. Your chances are also higher if you are on any kind of fertiilty drug. But there is no way to 'make' this happen, regardless.
Best wishes!