There are really only three DIY SMT soldering techniques that I am aware of
1) fine-tipped soldering iron and magnifying glass
2) a toaster / reflow oven
3) a reflow hotplate
However, if one needs to solder a BGA device, then the latter two methods are are the only ones possible.
I just thought I would post links ot a couple of interesting articles I found on techniques 2 and 3.
DIY techniques can save you literally thousands of dollars - I've seen reflow ovens for sale for over $2500 and reflow hotplates for over $1200 !
I also just thought that I would mention, that it is possible to use a regular computer or laptop as a PID controller, if one connects uses a solid-state relay for current control of the toaster / reflow oven, with an accurate temperature sensor.
There's also a great tutorial for applying solder paste to a PCB with stencil . Always check whether or not the BGA solder balls contain flux - in many cases they do not, and you should apply a bit of flux to the PCB before baking it.