A good point, and one not often, nor clearly mentioned, that a circuit diagram in no way represents the physical properties of the components involved unless explicitly stated. The shape, size, layout, colour...anything at all is not the fuction of a circuit diagram.
Often (as the good Dr. has above) there will be a pin-out of the devices used, but in more complex diagrams these are often omitted to save space and left to the user to find out the data. This simply involves downloading the datasheet for the device, Farnell, RS and many others provide those links within their own web-site of the device.
Alternatively a simple Google will turn up what you need, e.g. "LM358 datasheet", "BC548 datasheet". Omit suffixes too, search on LM317 not LM317D2T-TR
Or if you know the manufacturer (LMxxx is usually National Semiconductor for example, but second-sourced by many others) use this very useful link for semiconductors...
http://sdw.bgs.nu/
For the tube-heads amongst us (though most will know of this), there's this...
http://www.tubedata.org/
Steve A.