Electrical – How to identify this SMD device from the code on top of the component

1. KT3 is a BAS21 diode. Link goes to the data sheet, includes information on similar diodes (BAS19/BAS20/BAS21) and the date code (yours seems to be July 2007)
2. CVL seems to be a transient voltage suppressor. The link goes to a site with lots of SMD codes.
3. A48 could be one of several things. You'll need to compare the connections of your chip to the datasheets of the various parts that may be marked A48 (most likely a voltage regulator.)
4. 1PX looks like its a voltage detector.

For the 1PX, the dot shows pin 1. Putting Pin1 at the lower left mean you read it 1PX instead of other combinations you tried (K and stuff.)

Sorry, I can't give you any really good tips for finding the codes.
The linked site helps, and there are others like it, but it all comes down to having good google-fu.
Google, get ideas, check the circuit against the datasheets.

The part is connected to pin 5 of the USB connector, which is the 5V supply from USB. It is most likely to be a fuse: either a PTC resetable fuse or a non-resettable fuse. Its marking are consistent with a SMT fuse, although to understand the marking you would need to know the manufacturer of the fuse. It is unlikely to be an inductor or ferrite bead, since those parts are usually unmarked.

After the fuse is a diode of some sort connected between the 5V supply and Ground. This is probably a TVS diode to protect the device against voltage transients.

If you follow the PCB trace it then passes through part which is probably a ferrite bead which is used to reduce EMI emissions. SMT ferrite beads are usually unmarked.