Bitmap to Vector

Not sure if this is the right forum for this or not(feel free to move it if you want, mods).

What is the best and quickest way to convert a bitmap image to a vector image? What program would you use and how would you do it?

Also, anyone know a good way of “blowing up” images…i’ve seen people turn 8x10 photos into billboards…would love to know how to do so.