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Kane, It depends on your requirements. You may either use fixed or variable voltage type, 3 terminal regulators.Example,if you use a fixed regulator such as 7809, the out put current is limited to 1amp.On the other hand, a variable voltage regulator such as LM338K, you will be able to get voltages down from 1.2 to 32v max depending on you input voltage with a maximum current of 5amp. The LM 396K with voltages from 1.2 to 15v and a current of 10amp max. In high current applications it is essential to provide adequate heat sinking. Failure to observe this precaution may result in premature current limiting or output voltage foldback due to thermal shutdown.
You can get a .1A regulator in much smaller packages. For example you could find a .1A reg in a TO-92 (or tiny SOT-23) package instead of the larger TO-220 for a 1A.
For a hobbiest there really is no reason to use a smaller current rating.
Another important thing to keep in mind when selecting a regualtor is the power dissipation. If you want a 3.3V supply regulated from a 12V supply at 1 Amp that is (12V-3.3V)*1A = 8.7W which is quite a bit of power to disipate in your regulator. 8.7W will reqire a fair sized heat sink on a TO-220 package or better. So don't just trust the current rating.