EDIT
Everyone can try to make an emulator for this phone http://www.gsmarena.com/htc_chacha-3787.php to see what I mean. The icons will be huge and the screen you get is not the same as on the real phone.
Here are the specs:
Display: TFT capacitive touchscreen, 256K colors
Size: 480 x 320 pixels, 2.6 inches (~222 ppi pixel density)
I tried to make an emulator for a specific Android phone, but the resolution was all wrong. So I will write what I did, and I hope someone will correct me.
First I go to GSMArena.com and pick some phone (I'll use a random here)
Sony Ericsson Xperia PLAY
I see that the size of the screen is 480x854 with a density of 245 ppi.
Then I create a new emulator machine with WVGA854 (LARGE type of screen) and I manually set the DPI to 245 (HDPI).
Is this correct: 245ppi == 245dpi?
Sometimes this works, but most times, I get big icons on a small screen, especially when I try to make an emulator for NORMAL screen phones which have resolution of around 240ppi. When I compare such screen on the emulator with the original phone screen snapshots, I see it's just not the same.
So what is the best way, to create an emulator, for a specific mobile phone, so that it exactly match the manufacturer's screen size and pixel density?