ok, not really sure if you are simply designing a circuit using smd parts, or if you are trying to determine the exact parts used on an existing board.
If it's the latter, then it's really not straightforward.
A quick starter on smd parts (sorry, couldn't find your part FT9819) :
as an example, an
ATmega328P is the general part no, however, this is available in several packages:
ATMEGA328P-PU is DIL (Dual inline 0.1")
ATMEGA328P-AU is smd type TQFP-32 (32 is no of pins)
etc
often, the last additional chars determine the package
smaller parts obviously won't have this or even their part no printed on them
the list of packages is quite extensive and constantly growing.
onsemi have a pdf (link has been removed from their site) with most of the std ones named
common ones are SOT-23 (often used for transistors/diodes/voltage regulators) and SOT23-5 (often for v-regs) and bigger ones SO-8, SO-16, SO-20 etc
be aware that there are often std & wide versions of some of the SO** chips so it pays to check the datasheet of the part in question